If you run a small limited company, the key dates can feel scattered. Companies House wants one thing, HMRC wants another, and your own Self Assessment runs on a different clock again. This guide brings them together in one place. The first half covers your company. The second half covers you as an individual, including Self Assessment and payments on account.
Most company deadlines are not fixed calendar dates. They depend on your company's year end, so we explain how to work each one out rather than listing dates that may not apply to you.
Why company deadlines depend on your year end
Every limited company has an accounting reference date. This is the date its financial year ends each year, and it is often called the year end. Companies House sets it when you form the company, and you can change it in some cases.
Almost every company deadline counts forward from that date. So a company with a 31 March year end has very different due dates from one with a 31 December year end. Once you know your year end, you can build your whole calendar from it.
Heads up - You can find your company's year end and next filing dates on the free Companies House register. Search for your company name and check the filing history and overview pages.
Small company deadlines at a glance
Here are the main deadlines for a private limited company that is not large enough to pay Corporation Tax in instalments. Corporation Tax is the tax your company pays on its profits.
| What | Who it goes to | When it is due |
|---|---|---|
| Annual accounts | Companies House | 9 months after your year end |
| Corporation Tax payment | HMRC | 9 months and 1 day after the end of your accounting period |
| Company Tax Return (CT600) | HMRC | 12 months after the end of your accounting period |
| Confirmation statement | Companies House | Within 14 days of the end of each 12-month review period |
| VAT returns (if VAT registered) | HMRC, through Making Tax Digital software | Usually 1 month and 7 days after each VAT period ends |
Your Corporation Tax is due before your tax return is. Many people get caught out because they assume the payment and the return share one deadline.
Annual accounts for Companies House
Your company must file annual accounts with Companies House every year. For a private company, you usually have 9 months from your year end to do this.
Your first accounts work a little differently. If your company is new, the deadline is usually 21 months after the date it was formed. This is because the first accounting period can be longer than 12 months.
Companies House charges an automatic penalty if your accounts arrive late. The amount rises the later you file. So it is worth aiming to file well before the deadline, not on the day itself.
Corporation Tax payment and the CT600 return
You deal with HMRC separately from Companies House. There are two parts.
Paying your Corporation Tax
For most small companies, you pay Corporation Tax 9 months and 1 day after the end of your accounting period. HMRC does not send you a bill first. You work out what you owe and pay it yourself. HMRC charges interest if you pay late.
Filing your CT600
The CT600 is your Company Tax Return. You file it online with HMRC, along with your accounts and tax calculations. It is due 12 months after the end of your accounting period. You must file it even if your company made a loss or has no tax to pay, as long as HMRC has asked you to file.
HMRC charges penalties for late returns, and these can grow the longer a return is outstanding.
Heads up - An accounting period for Corporation Tax cannot be longer than 12 months. If your first set of accounts covers more than 12 months, you will usually need to file two tax returns for that stretch of time. Tax optimiser will just need one accounting period and by able to split your submissions in to 2 separate returns. Your accountant can help you work out the split.
The confirmation statement
The confirmation statement tells Companies House that the information it holds about your company is up to date. That includes details such as your directors, shareholders, registered office and people with significant control.
You must file one at least once every 12 months. You have 14 days after the end of your review period to file it. Your review period usually starts from the date your company was formed, or from the date of your last statement.
There is a filing fee, and it is not tied to your year end at all. So it is easy to forget. We suggest you add it to your calendar as its own separate reminder.
VAT and Making Tax Digital quarters for companies
Making Tax Digital (MTD) is HMRC's programme for moving tax records and returns online. It means you keep digital records and send returns using software that connects to HMRC.
For limited companies, MTD currently applies to VAT. If your company is VAT registered, you must keep digital VAT records and file your VAT returns through MTD-compatible software. Most businesses file VAT returns every quarter.
Your VAT quarters are set by HMRC when you register, and they do not have to match your company year end. The return and payment are usually due 1 month and 7 days after the end of each VAT period. If you pay by Direct Debit, HMRC collects the payment a few days after the deadline.
Making Tax Digital for Income Tax does not apply to limited companies. It applies to individuals, which we cover in the Self Assessment section below.
A worked example with a 31 March year end
Let us put it all together for a company with a 31 March year end and standard calendar-quarter VAT periods.
| Deadline | Due date for the year ending 31 March |
|---|---|
| Accounts to Companies House | 31 December of the same year |
| Corporation Tax payment | 1 January of the following year |
| CT600 to HMRC | 31 March of the following year |
| VAT return for quarter to 31 March | 7 May |
| VAT return for quarter to 30 June | 7 August |
| VAT return for quarter to 30 September | 7 November |
| VAT return for quarter to 31 December | 7 February |
| Confirmation statement | Depends on your review period, not your year end |
You can use the same approach for any year end. Count 9 months for accounts, 9 months and 1 day for payment, and 12 months for the CT600.
Self Assessment deadlines for individuals
Self Assessment is the system HMRC uses to collect Income Tax from people whose tax is not all taken through PAYE (the system that takes tax from wages). It applies to many sole traders, landlords and company directors who take dividends.
If you run a company, your personal tax is completely separate from your company's tax. So you may have both calendars to keep track of.
Unlike company deadlines, Self Assessment dates are fixed. They are based on the UK tax year, which runs from 6 April to 5 April.
| Date | What happens |
|---|---|
| 5 October after the tax year | Deadline to register for Self Assessment if you have not filed before |
| 31 October after the tax year | Deadline for paper returns |
| 30 December after the tax year | Deadline to file online if you want tax under a certain amount collected through your PAYE tax code |
| 31 January after the tax year | Deadline for online returns, paying any balance owed, and your first payment on account for the current year |
| 31 July after that | Your second payment on account |
Late filing and late payment each bring their own penalties, plus interest on tax paid late. If you are struggling to pay, contact HMRC early. It may agree a payment plan, often called Time to Pay.
How payments on account work
Payments on account are advance payments towards next year's tax bill. They can be confusing at first, so here is the plain version.
If your last Self Assessment bill was above a set amount, HMRC usually asks you to pay towards the next year in two instalments. Each one is normally half of your previous year's bill. You pay the first on 31 January and the second on 31 July.
You do not usually need to make payments on account if your last bill was below HMRC's threshold (currently £1,000), or if most of your tax was already collected at source, for example through PAYE.
The balancing payment
After the tax year ends, you file your return and work out your actual bill. If your payments on account were less than what you owe, you pay the difference by 31 January. This is called the balancing payment.
If you paid too much, HMRC will refund you or set the extra against your next bill.
Why your first year can feel expensive
In your first year of paying through Self Assessment, you may owe your full bill for that year plus your first payment on account for the next year, all on the same 31 January. This can come as a shock. Setting money aside through the year helps a lot.
Heads up - If you expect your income to fall, you can ask HMRC to reduce your payments on account. But be careful. If you reduce them too far and end up owing more, HMRC will charge interest on the shortfall.
Making Tax Digital for Income Tax and quarterly updates
Making Tax Digital for Income Tax is coming in from April 2026 for sole traders and landlords with qualifying income above a set level. HMRC plans to lower that level in later years, so more people will join over time. Check the current rules to see when it applies to you.
If you are in scope, you will keep digital records and send quarterly updates to HMRC using compatible software. These updates are summaries of your income and expenses, not full tax returns.
| Quarter covers | Update due |
|---|---|
| 6 April to 5 July | 7 August |
| 6 July to 5 October | 7 November |
| 6 October to 5 January | 7 February |
| 6 January to 5 April | 7 May |
You will still need to confirm your final figures after the tax year ends, by 31 January. Payment dates, including payments on account, stay the same as they are today.
Tips for staying on top of every deadline
- Write down your year end first. Every company deadline follows from it.
- Keep company and personal dates separate. Use two lists or two colours so nothing gets mixed up.
- Set reminders well ahead. A month's warning gives you time to gather paperwork calmly.
- Put money aside as you go. A separate savings account for tax makes January and July far less stressful.
- Keep your records digital. It makes VAT, Making Tax Digital and year-end accounts much quicker.
- Talk to HMRC early if you are stuck. It is usually more flexible when you get in touch before a deadline rather than after.
Bringing it all together
Deadlines feel much more manageable once they are in one place. For your company, start from your year end and count forward: 9 months for accounts, 9 months and 1 day for Corporation Tax, 12 months for the CT600. Add your confirmation statement and VAT quarters as separate reminders. For you personally, remember 31 January and 31 July, and plan ahead for payments on account.
If you would like help keeping track, TaxOptimiser can bring your company filings, VAT returns and Making Tax Digital updates into one clear view, so you always know what is coming next.