How to register for Corporation Tax in the UK: the complete guide for limited companies

Every year, HMRC issues late-filing penalties to thousands of UK limited companies that either registered for Corporation Tax too late or never registered at all. The amounts are not trivial — and the interest compounds quietly in the background while the founder assumes everything is fine because Companies House has not complained. The two regulators operate on completely separate clocks, and the Corporation Tax clock is the one that catches people out.

Here is the part that trips up most first-time founders: incorporating your company is not the same as registering it for Corporation Tax. When you incorporate, Companies House automatically notifies HMRC, and HMRC usually sets up a Corporation Tax record and posts a Unique Taxpayer Reference (UTR) to your registered office. But that is HMRC noting that your company exists — it does not tell HMRC when (or whether) you have started trading. The obligation that sits with you is to tell HMRC your company is active within three months of starting business activity, unless you have already done so through HMRC's online registration service. That distinction matters because it determines when your three-month window opens — and getting it wrong in either direction creates problems. Tell HMRC too early and it expects a CT600 return for a period in which you had no activity. Tell HMRC too late and you are already in breach before you file your first invoice.

This guide explains exactly how to register for Corporation Tax for a UK limited company — when the deadline kicks in, what you need, the step-by-step HMRC registration process, and what happens at every stage after that. If you have just incorporated and are wondering which tax registrations you actually need right now, start here.

What is Corporation Tax and who pays it?

Corporation Tax is the tax on the taxable profits of a UK limited company. It covers trading profits, investment income, and chargeable gains. Unlike income tax, which applies to individuals, Corporation Tax applies to the company as a separate legal entity. The current main rate is 25% for companies with profits above £250,000, with a small profits rate of 19% for companies with profits up to £50,000. Companies in between pay a marginal rate.

Every UK limited company that is trading or earning income must register for Corporation Tax and file an annual CT600 return with HMRC. There is no exemption based on size, turnover, or the number of directors. Even a single-director company earning modest consultancy fees is within scope.

The only exception is genuinely dormant companies — those with no significant accounting transactions in the period. If your company is dormant, you can notify HMRC and they will not require a CT600 until you become active again. We covered dormant-company compliance in detail in our dormant company checklist.

When you need to register for Corporation Tax

You must tell HMRC your company is active within three months of starting business activity. That phrase — "business activity" — is doing the heavy lifting, and HMRC interprets it broadly. HMRC's own guidance lists activities such as buying, selling, advertising, renting a property, and employing someone as signs that a company has become active. In practice, HMRC may treat any of the following as an indicator that your company is now within the charge to Corporation Tax:

• Issuing invoices or receiving payment for goods or services
• Receiving income through the company — including income such as affiliate commissions, royalties, or interest
• Entering a business contract — a lease, a supplier agreement, a client engagement letter
• Buying or selling business assets, including stock, equipment, or intellectual property
• Advertising or marketing your products or services
• Hiring employees or engaging contractors through the company
• Renting property for business use
• Earning interest on a business bank account

No single item is a rigid, automatic trigger in isolation — what matters is whether, taken together, your activities show the company has started to trade or otherwise come within the charge to Corporation Tax. If you are unsure whether a particular step has made your company active, it is worth confirming the start date with your accountant rather than guessing.

Notice what is not on that list: incorporating the company. Incorporation alone does not trigger the Corporation Tax registration obligation. If you set up a company in January to reserve a name but do not start trading until June, your three-month window opens in June. This is the single most misunderstood deadline in UK company compliance — we see founders register on the day of incorporation (too early) and founders who assume HMRC will contact them when it is time (too late, and HMRC often does not chase until penalties have already accrued).

What happens if you incorporated but are not yet trading?

If your company exists on the Companies House register but has not started any business activity, you are not yet required to register for Corporation Tax. However, you are still a live company with Companies House obligations — your confirmation statement is still due every 12 months, and your first annual accounts are still due 21 months from the date of incorporation. Those deadlines run from incorporation, not from trading. Our post-incorporation checklist walks through everything that applies from day one.

Can you register before you start trading?

Yes — and in some cases it makes sense, particularly if you know exactly when trading will begin. But register too far in advance and HMRC will expect a CT600 return covering that period. If the return shows zero activity, that is fine administratively, but it creates an extra filing obligation and potential confusion when your accountant is reconciling periods. The cleanest approach is to register as soon as business activity begins, giving yourself the full three-month window without creating unnecessary empty return periods.

What you will need before you register

Before you start the HMRC Corporation Tax registration process, gather everything below. Having it ready makes the registration faster and avoids having to abandon the form halfway through.

From Companies House

• Company name and registration number — exactly as they appear on the Companies House register
• Date of incorporation
• Registered office address
• Business address (if different from the registered office)
• Nature of business — your SIC code description (see our SIC codes guide if you are unsure which applies)

You need to determine

• Date business activity started (or will start) — this sets your first accounting period for Corporation Tax purposes
• Accounting reference date — usually the last day of the month in which the company's anniversary of incorporation falls, unless you have changed it
• Director details — names, addresses, National Insurance numbers
• Estimated annual turnover and number of employees

In most cases your UTR will already have been issued automatically. HMRC normally posts it to your registered office within around 14 days of incorporation, before you do anything — so you usually do not need to wait for or chase it before you can plan your registration. More on that below.

Understanding your Unique Taxpayer Reference (UTR)

Your company's Unique Taxpayer Reference (UTR) is a 10-digit number assigned by HMRC to identify your company for tax purposes. It is the single most important reference number you will use in your dealings with HMRC — required for filing your CT600 return, making Corporation Tax payments, and activating the Corporation Tax service on your Government Gateway account.

How you get your UTR

When you incorporate a company, Companies House automatically notifies HMRC, and HMRC normally issues your UTR without you having to ask for it. In most cases HMRC posts the UTR letter to your company's registered office address within around 14 days of incorporation, though it can occasionally take longer. The letter is sent by post — it is not emailed and is not available online until you activate your account with it. If the letter is lost or never arrives, you can ask HMRC to send a replacement.

Important: a UTR does not mean you are registered for Corporation Tax

This is a common source of confusion. Receiving a UTR means HMRC knows your company exists — it does not mean Corporation Tax is active on your account. You still need to complete the registration process, set up your Government Gateway account, and activate the Corporation Tax service. Think of the UTR as your company's tax identity number. Registration is the separate step where you tell HMRC when you started trading and confirm your accounting period.

What to do if your UTR has not arrived

If more than four weeks have passed since incorporation and you have not received a UTR letter, contact HMRC's Corporation Tax helpline to request one. A replacement letter typically takes another two to three weeks. In the meantime, you cannot activate Corporation Tax online, file a CT600, or make a payment — so do not wait.

This is one of the practical reasons your registered office address needs to be monitored daily. If the UTR letter sits in an unopened pile — or worse, at a home you have moved away from — you will not know your reference number, and HMRC deadlines do not pause while you chase it. We covered this in detail in our guide on the risks of using your home as a registered office.

How to register for Corporation Tax: the step-by-step process

Registration is done through HMRC, not Companies House. The two bodies share certain data, but Corporation Tax registration is a separate process that you must initiate yourself. Here is how it works, step by step.

Step 1: Check whether you have received your UTR

Before starting the online registration, check whether HMRC has already posted your UTR to your registered office. As explained above, HMRC is automatically notified by Companies House when you incorporate, and a UTR letter is usually sent within a few weeks. Having your UTR ready makes the process smoother — you will need it to activate the Corporation Tax service later.

If your UTR has not arrived yet, you can still begin the registration process. HMRC will issue one as part of registration if they have not already. But do check your post first — starting the process with your UTR in hand avoids duplication and delays.

Step 2: Set up a Government Gateway account for your company

You need a Government Gateway account for the company. This is separate from any personal Government Gateway account you may have for Self Assessment. Go to the HMRC online services page, select "Organisation", and create new sign-in details specifically for the company.

Why this matters: Government Gateway is the portal through which all your HMRC interactions happen — filing returns, making payments, viewing deadlines. Without it, you cannot manage Corporation Tax online.

Common mistake: Using your personal Government Gateway account. A personal account is linked to your individual tax affairs (Self Assessment, personal tax). The company needs its own account — Corporation Tax, PAYE, and VAT are all managed through the company's Gateway credentials.

Many companies manage Corporation Tax themselves through their own Government Gateway (business tax account). You do not have to do it this way, though: an accountant or tax adviser can register and manage Corporation Tax on your behalf through HMRC's authorised agent services. If you appoint an agent, they use their own agent account and you authorise them to act for the company — you do not need to share your company Gateway login with them.

Step 3: Add Corporation Tax to your Government Gateway account

Once logged in to the company's Government Gateway, you need to add Corporation Tax as a service. This is the step that actually registers the company for Corporation Tax with HMRC. Select "Add a tax, duty or scheme", choose Corporation Tax, and enter your company's UTR and registration number when prompted.

Why this matters: Having a Government Gateway account is not the same as being registered for Corporation Tax. You must explicitly add the CT service. Until you do, HMRC's online system does not know you intend to file Corporation Tax returns through this account.

Common mistake: Assuming you are "registered" because you have a Government Gateway account or because you received a UTR. Neither of those completes the process. Registration happens when you add Corporation Tax to your account and provide your trading details.

Step 4: Enter your trading start date

During registration, HMRC will ask when the company started (or intends to start) doing business. Enter the date accurately — this sets the start of your first Corporation Tax accounting period. All of your future filing and payment deadlines flow from this date.

Why this matters: Getting the trading start date wrong creates misaligned accounting periods. If you enter a date earlier than actual trading began, HMRC expects a CT600 covering a period of inactivity. If you enter a date later than trading actually started, you risk late registration consequences.

Common mistake: Using the incorporation date when trading started later — or vice versa. Your incorporation date and trading start date are often different. If you incorporated in January but did not send your first invoice until April, the trading start date is April.

Step 5: Confirm your accounting period

HMRC will ask you to confirm or adjust your accounting period end date. By default, this aligns with your Companies House accounting reference date (ARD) — typically the last day of the month in which the company's anniversary of incorporation falls.

Why this matters: Your accounting period determines when your CT600 return is due and when your Corporation Tax payment is due. Getting this aligned correctly from the start avoids confusion and duplicate filings.

Common mistake: Not realising that if your first Companies House accounting period exceeds 12 months, HMRC will split it into two Corporation Tax periods — one of 12 months and one covering the remainder. That means two CT600 returns and two payment deadlines in your first year. Discuss your ARD with your accountant early to avoid surprises.

Step 6: Complete registration and wait for your activation code

Submit the registration. HMRC will then post an activation code to your registered office address. This is a separate letter from the UTR — it arrives after registration and is needed to fully activate the Corporation Tax service on your Government Gateway account.

Why this matters: Until you enter this activation code, you cannot file your CT600 online or view your Corporation Tax account details. The code confirms that the person managing the account has access to the registered office.

Common mistake: Not watching for the activation code letter. It is a separate letter from the UTR, arriving later. If you have already received and filed away your UTR letter, you may not be expecting another letter from HMRC — but this one is equally important.

HMRC will also ask during registration whether the company has taken over another business and whether you need to register for PAYE or VAT at the same time. You may still see older guidance refer to a paper form called the CT41G, which HMRC historically posted to new companies to collect these details. For the vast majority of companies that route has been replaced by the online service — you do not need to find, request, or complete a CT41G, and registering online is faster and confirms your details immediately.

Key deadlines after registration

Once registered, your company enters a rhythm of annual deadlines. These run from the end of each accounting period, not from the calendar year. Getting them confused is the single most expensive compliance mistake a small company can make. Here is the summary:

The CT600 return

Your Company Tax Return (CT600) must be filed with HMRC within 12 months of the end of the accounting period it covers. The CT600 includes the company's full computation of taxable profits, capital allowances, and the tax due. Most companies file through their accountant using commercial software, but the legal responsibility sits with the directors.

Corporation Tax payment

The tax itself must be paid within 9 months and 1 day of the end of the accounting period. Note that the payment deadline is earlier than the filing deadline — you must pay the tax three months before the return is due. This catches founders out regularly: the accountant has until month 12 to finalise the return, but the money needs to be with HMRC by month 9. If you are unsure of the exact amount, you can make a payment on account and adjust later.

First-year accounts: the extended deadline

Your first set of annual accounts at Companies House is due 21 months from the date of incorporation. Subsequent accounts are due 9 months after the accounting reference date. These are Companies House deadlines, separate from HMRC — but the underlying financial statements overlap, which is why most accountants prepare both the statutory accounts and the CT600 together. Our annual accounts guide covers the Companies House side in detail.

How your accounting reference date affects these deadlines

Your accounting reference date (ARD) determines the end of each financial year for your company. By default, Companies House sets this as the last day of the month in which your company's anniversary of incorporation falls. For example, if you incorporated on 15 March 2026, your ARD would be 31 March. Your first accounting period runs from incorporation to the first ARD — which could be up to 18 months.

For Corporation Tax purposes, HMRC aligns your tax accounting period to your ARD, but a single CT accounting period cannot exceed 12 months. If your first Companies House accounting period is longer than 12 months, HMRC will split it into two Corporation Tax periods — one of 12 months and one covering the remainder. That means two CT600 returns and two payment deadlines for your first year. Discuss your ARD with your accountant early to avoid surprises.

What happens if you do not register on time

There is no separate HMRC penalty purely for late Corporation Tax registration. However, late registration almost always triggers a chain of consequences — and that chain is where the real cost sits.

The cascading effect of late registration

If you register late, your CT600 return is already overdue from the moment you register. Your Corporation Tax payment may also be late. Both carry automatic penalties and interest — and they start from the original deadline, not from when you eventually registered. A founder who registers six months late is not starting fresh; they are starting with six months of accumulated penalties and interest already owed.

HMRC can also open a compliance check into companies that failed to notify on time. While rare for small companies, this creates additional administrative burden and stress. Beyond HMRC, a company with outstanding penalties may face difficulties with lenders, investors, or clients who run credit checks — unresolved HMRC debts do show up and they raise questions.

Late CT600 filing penalties

HMRC's penalty regime for Corporation Tax is blunt and automatic. There is no grace period and no "first offence" concession. If your CT600 return is filed late, HMRC charges:

• 1 day late — £100 penalty
• 3 months late — another £100 penalty (£200 total)
• 6 months late — HMRC estimates your Corporation Tax bill and adds a penalty of 10% of the unpaid tax
• 12 months late — a further 10% of any unpaid tax

If your company files late three times in a row, the initial £100 penalties each increase to £500. That escalation is where small companies get hurt — a pattern of late filings turns minor penalties into a running bill.

Late payment interest

On top of the filing penalties, HMRC charges interest on unpaid Corporation Tax from the day after the payment deadline (9 months and 1 day after the accounting period ends). The interest rate fluctuates with the Bank of England base rate and is currently well above what a savings account would earn — it compounds daily, and it is not deductible against the company's profits.

Companies House penalties run in parallel

Do not confuse HMRC late-filing penalties with Companies House late-filing penalties — they are separate systems with separate penalties. Late annual accounts at Companies House attract their own fixed penalties starting at £150 and climbing to £1,500 for private companies. A company that files both the CT600 and the statutory accounts late is paying two sets of penalties simultaneously.

Do you also need to register for VAT or PAYE?

Corporation Tax is the baseline registration, but it is not the only HMRC obligation your company may have. Two other registrations frequently trip up new founders.

VAT registration

VAT registration is mandatory only once your taxable turnover exceeds £90,000 in any rolling 12-month period, or you expect to exceed it in the next 30 days. Below that threshold, registration is voluntary. Many founders register voluntarily to reclaim VAT on startup costs, but it comes with the obligation to file quarterly VAT returns and charge VAT on invoices — so it is not automatically a good idea for every early-stage company.

VAT registration is not triggered by incorporation. You can incorporate a company, register for Corporation Tax, and operate for years without ever needing to register for VAT, provided you stay below the threshold.

PAYE registration

If you intend to pay salaries — to employees or to yourself as a director drawing a regular wage — you must register for PAYE before the first payday. Ideally, register at least two weeks before that first payment to allow HMRC processing time. PAYE is not triggered by incorporation, by appointing a director, or by paying dividends — only by paying salaries.

Many single-director companies pay the director entirely in dividends with a small salary below the National Insurance threshold. That salary still requires PAYE registration. If you are paying no salary at all and taking only dividends, PAYE registration is not needed. For a full walkthrough of what to set up in your first few weeks, see our post-incorporation checklist.

Common mistakes when registering for Corporation Tax

Corporation Tax registration is straightforward on paper, but the timing and sequencing is where companies go wrong. These are the patterns we see repeatedly.

1. Assuming HMRC will tell you when to register. HMRC receives notification when you incorporate, but it does not reliably chase you to register for Corporation Tax. The responsibility is entirely on the directors. By the time HMRC does write to you, the three-month window may have already closed.
2. Registering on the day of incorporation when you are not yet trading. This creates an accounting period that starts immediately, and HMRC will expect a CT600 covering that period even if the company had no activity. It is not catastrophic — you file a nil return — but it is unnecessary admin and can confuse your accounting reference date alignment.
3. Not knowing when "business activity" actually started. If you signed a client contract in March but did not invoice until May, the activity started in March. If you bought a domain and paid for hosting through the company account in January, that is arguably January. Pin down the date early with your accountant so your registration and accounting periods are clean.
4. Missing the UTR letter because the registered office is not monitored. The UTR is posted to the registered office — not emailed, not available online until you activate the account with it. If the letter is lost, you have to request a replacement, which takes another two to three weeks. In the meantime, you cannot file or pay.
5. Confusing the payment deadline with the filing deadline. Tax is due at 9 months and 1 day. The CT600 return is due at 12 months. Pay late and interest accrues from day one. We see companies that file their return on time but pay three months late because they assumed both deadlines were the same.
6. Forgetting that Companies House and HMRC are separate systems. Filing your annual accounts with Companies House does not satisfy your CT600 obligation with HMRC (and vice versa). Both need separate filings, separate payments where applicable, and both have their own penalty regimes.
7. Assuming your company is already registered because HMRC sent a UTR. Receiving a UTR means HMRC knows your company exists. It does not mean Corporation Tax is active on your account. You still need to add Corporation Tax to your Government Gateway account, enter your trading start date, and confirm your accounting period. The UTR is your tax identity — registration is a separate process.

Practical setup: bank accounts and records

Business bank account

A business bank account is not legally required for a UK limited company. There is no statute that mandates it. However, from a Corporation Tax perspective, it is practically essential. Mixing personal and business transactions makes it significantly harder to compute taxable profits accurately, increases accountancy costs, and is a red flag if HMRC ever opens an enquiry. Most banks, lenders, and payment processors also require a dedicated business account before they will work with you.

If you have not opened one yet, do it before you start trading — it makes your Corporation Tax registration cleaner, your bookkeeping cheaper, and your accountant's life considerably easier.

Statutory records

Corporation Tax is one piece of a broader compliance picture. By the time you register with HMRC, your company should also have its statutory registers in order — these are the legally authoritative records of your company's structure:

• Register of members (shareholders)
• Register of directors
• Register of directors' residential addresses (private, not public)
• PSC register (People with Significant Control)
• Register of charges
• Register of secretaries (if one is appointed — private limited companies are not required to appoint a company secretary)

Your accounting records must be retained for at least 6 years from the end of the accounting period they relate to. The public Companies House record is not the legal record — your internal statutory registers are. If an HMRC enquiry, investor due diligence, or legal dispute arises, it is your books and registers that are examined first.

Identity verification: the 2025 change that affects everything

Under the Economic Crime and Corporate Transparency Act (ECCTA), directors and people with significant control (PSCs) must verify their identity with Companies House. Verification first opened on a voluntary basis on 8 April 2025, and became a legal requirement from 18 November 2025. From that date, identity verification is a compulsory part of incorporating a new company and of appointing new directors and PSCs.

For companies that already existed on 18 November 2025, there is a 12-month transition period. Existing directors must verify by the time they file their company's next confirmation statement (and provide their Companies House personal code with it), and existing PSCs have their own deadline tied to their circumstances — so most established companies will need everyone verified at some point before 18 November 2026. This is separate from HMRC registration, but it matters in context because, once it applies to your company, you will not be able to file certain changes — such as appointing a new director to help manage the company's tax affairs — until the people involved are verified.

Two lawful routes exist: directly via GOV.UK One Login (free) or through an Authorised Corporate Service Provider (ACSP) like Filing HQ. Verification is a one-off per person — it does not need to be repeated for each appointment or filing. Our identity verification guide covers the full process.

Your Corporation Tax timeline: what to do and when

Pulling all of this together, here is the practical timeline for a newly incorporated UK limited company from a tax and compliance perspective:

Immediately after incorporation

• Save your certificate of incorporation, company number, and authentication code
• Ensure your registered office address is being monitored for post
• Complete identity verification for all directors and PSCs
• Open a business bank account (not legally required, but practically essential)
• Watch for your UTR letter from HMRC — if it has not arrived within four weeks, contact HMRC to request one

When business activity starts

• Pin down the exact date activity began — this is your Corporation Tax trigger date
• Register for Corporation Tax with HMRC within 3 months
• Register for PAYE if you will be paying salaries (before the first payday)
• Consider voluntary VAT registration if it benefits your cash flow

Within 12 months of incorporation

• File your confirmation statement with Companies House (due every 12 months, online fee £50) — our confirmation statement guide explains the process
• Begin preparing your first set of accounts with your accountant

9 months and 1 day after accounting period ends

• Pay Corporation Tax to HMRC

12 months after accounting period ends

• File your CT600 return with HMRC

21 months after incorporation (first year only)

• File your first annual accounts with Companies House (subsequent years: 9 months after the ARD)

Frequently asked questions

Do I automatically get registered for Corporation Tax when I form a company?

Not fully. It helps to separate three things. Incorporation creates the company at Companies House. Companies House then automatically notifies HMRC, which usually sets up a Corporation Tax record and posts your company a UTR — that is HMRC registering that your company exists. The third step is telling HMRC your company is active (when it started trading and its accounting period), which you must do within three months of starting business activity. Receiving a UTR does not mean HMRC knows you have started trading, so you should not assume the company is "fully registered" just because the UTR has arrived. You can often complete this step at the point of incorporation if you form the company through the right route, but otherwise it is a separate online registration you initiate yourself.

Do I need to register for Corporation Tax if my company is not trading?

No. If your company has not started any business activity, you are not yet required to register for Corporation Tax. The obligation is triggered by business activity, not by incorporation. However, you should register within three months once activity begins — and remember that "business activity" is interpreted broadly by HMRC to include signing contracts, buying assets, advertising, and earning interest.

How long does it take to get a UTR?

You usually do not have to wait until you register for Corporation Tax to receive your UTR. Because Companies House notifies HMRC when you incorporate, HMRC normally posts the UTR to your registered office within around 14 days of incorporation, though it can occasionally take longer. The letter is posted, not emailed, so make sure someone is monitoring your registered office address. If it does not arrive, you can ask HMRC to send a replacement.

What is the difference between a UTR and a Government Gateway account?

Your UTR (Unique Taxpayer Reference) is your company's 10-digit tax identity number — HMRC uses it to identify your company across all tax matters. Government Gateway is the online portal where you manage tax services, file returns, and make payments. You need the UTR to activate Corporation Tax on your Gateway account, but they are separate things. Think of the UTR as your tax ID and Government Gateway as the website where you use it.

My company was auto-registered by HMRC — do I still need to do anything?

Yes. HMRC may assign a UTR automatically after Companies House notifies them of your incorporation, but that does not complete the Corporation Tax registration process. You still need to set up a Government Gateway account, add the Corporation Tax service, and confirm your trading start date and accounting period. Auto-registration means HMRC knows you exist — it does not mean your Corporation Tax obligations are set up and ready to manage.

What is the difference between the CT600 and annual accounts?

The CT600 is your Corporation Tax return filed with HMRC — it calculates your taxable profit and the tax owed. Annual accounts (also called statutory accounts) are filed with Companies House and provide a public financial snapshot of your company. They are prepared from the same underlying bookkeeping, but they go to different regulators, have different deadlines, and attract separate penalties if filed late.

Can I register for Corporation Tax, VAT, and PAYE at the same time?

Yes. During the Corporation Tax registration process, HMRC gives you the option to register for PAYE and VAT simultaneously. Whether you should depends on your circumstances — VAT is only mandatory above the £90,000 turnover threshold, and PAYE is only required if you are paying salaries.

Can my accountant register my company for Corporation Tax?

Yes. Accountants and tax advisers can register and manage Corporation Tax for you through HMRC's authorised agent services. The agent acts through their own HMRC agent account, and you authorise them to deal with HMRC on the company's behalf — you do not need to hand over your own company Government Gateway login. The legal responsibility for registering on time and filing the CT600 still rests with the company's directors, so it is worth confirming with your accountant exactly who is handling the registration and by when, rather than each side assuming the other has done it.

What if I miss the three-month registration deadline?

Register as soon as you realise you have missed it — do not wait until your accounts are ready. HMRC does not impose a separate penalty purely for late registration, but late registration almost always leads to a late CT600 filing and late payment, both of which carry automatic penalties and interest that run from the original deadlines. The longer you delay, the larger the bill. If you have a genuine reason for the delay, you can explain it to HMRC, and where a penalty is later charged for late filing you may be able to appeal if you have a reasonable excuse.

Is a business bank account legally required for Corporation Tax?

No. A business bank account is not legally required for a UK limited company. However, it is practically essential for accurate Corporation Tax computation — mixing personal and business transactions makes bookkeeping difficult, increases accountancy costs, and raises red flags if HMRC conducts an enquiry.