Incorporating a UK company takes about ten minutes online and costs GBP 100. Everything that follows takes considerably longer. Your first year is the messiest one, because the accounting period rarely lines up with anything convenient, the deadlines are set by two different government bodies, and several of them fall a long way after the work they relate to.
This guide sets out every filing and payment obligation a new UK company faces in its first twelve to twenty-one months, with the rates that apply in the 2026/27 tax year and the financial year beginning 1 April 2026. It ends with a full calendar for a company incorporated on 12 September 2025, which you can shift to your own incorporation date.
What incorporating actually starts
Registering at Companies House creates a separate legal person. From that moment the company, not you, owns the contracts, the bank account and the profits, and the company has its own filing obligations regardless of whether it trades. A dormant company still files accounts and a confirmation statement.
Companies House fees changed on 1 February 2026: digital incorporation is now GBP 100 and the confirmation statement is GBP 50, per the Companies House fee announcement. Since 18 November 2025, identity verification has been compulsory for all directors and people with significant control. You must verify before you can be appointed, and unverified directors cannot file a confirmation statement, so deal with it in week one rather than the week the statement is due.
HMRC is told about the incorporation automatically, and within about two weeks you should receive a Unique Taxpayer Reference for the company. You then have three months from the date the company starts trading to tell HMRC it is active.
Your first accounting period is almost certainly longer than a year
Companies House sets your accounting reference date as the last day of the month in which you incorporated, one year later. Incorporate on 12 September 2025 and your first accounting reference date is 30 September 2026, giving a first period of 12 months and 19 days.
That creates a problem, because a corporation tax accounting period can never exceed 12 months. Your single set of accounts therefore has to be split into two corporation tax periods: 12 September 2025 to 11 September 2026, and 12 September 2026 to 30 September 2026. You file two CT600 returns for one set of accounts, with two different payment dates. This catches out nearly every first year director who tries to file without an accountant.
You can avoid it by shortening the accounting reference date to 31 August 2026 before the period ends, giving a single period of just under 12 months. Shortening is free and can be done as often as you like. Extending is restricted to once every five years.
Corporation tax: rates, marginal relief and short periods
For the financial year starting 1 April 2026 the rates are unchanged, as confirmed in HMRC's corporation tax rates and allowances.
| Taxable profits | Rate | Notes |
|---|---|---|
| Up to GBP 50,000 | 19% small profits rate | Limit divided by number of associated companies |
| GBP 50,001 to GBP 250,000 | 25% less marginal relief of 3/200 | Effective rate rises from 19% to 25%, marginal rate 26.5% |
| Over GBP 250,000 | 25% main rate | No marginal relief |
Both limits are pro-rated for accounting periods shorter than 12 months. For a 19 day period the GBP 50,000 lower limit becomes GBP 50,000 times 19/365, or GBP 2,602.74, and the upper limit becomes GBP 13,013.70. A stub period with GBP 4,700 of profit is therefore in the marginal relief band, not the 19 per cent band, which surprises people who assume small stub periods are always taxed at 19 per cent.
Corporation tax is due 9 months and 1 day after the end of each accounting period. The CT600 return is due 12 months after the end of the period of account, so both returns in a split first year share the same filing date even though the payment dates differ.
Worked example: first year corporation tax
Take the 12 September 2025 company. In the first 12 month period it invoices GBP 120,000, has GBP 18,000 of allowable costs, pays the director a GBP 12,570 salary and GBP 1,135.50 of employer National Insurance. Profit is GBP 120,000 minus GBP 18,000 minus GBP 12,570 minus GBP 1,135.50, which is GBP 88,294.50.
Tax at 25 per cent is GBP 22,073.63. Marginal relief is 3/200 times (GBP 250,000 minus GBP 88,294.50), which is 0.015 times GBP 161,705.50, or GBP 2,425.58. Corporation tax due is GBP 19,648.05, an effective rate of 22.25 per cent, payable by 12 June 2027.
The 19 day stub period to 30 September 2026 makes GBP 4,700 of profit. Tax at 25 per cent is GBP 1,175. Marginal relief is 0.015 times (GBP 13,013.70 minus GBP 4,700), which is GBP 124.71. Corporation tax due is GBP 1,050.29, payable by 1 July 2027. First year corporation tax across both periods is GBP 20,698.34. You can check your own figures with our corporation tax calculator.
Companies House: accounts and the confirmation statement
First accounts are due within 21 months of the date of incorporation, or three months from the accounting reference date if that is later. For a 12 September 2025 incorporation that is 12 June 2027. In every subsequent year the deadline is nine months after the accounting reference date.
The confirmation statement is a separate and much simpler filing that confirms your registered office, directors, shareholders, people with significant control and SIC codes. The first review period ends 12 months after incorporation, and the statement is due within 14 days of that. For our example that means a review period ending 11 September 2026 and a filing deadline of 25 September 2026. It is due even if nothing has changed and even if the company has never traded.
From 1 April 2027, small and micro-entity accounts must be filed using commercial software. Web filing and paper filing are being withdrawn, so if you have been planning to type your accounts into the Companies House portal, budget for software or an accountant.
PAYE: register before the first payday, not after
If the company pays anyone, including you as a director, above the lower earnings limit, it must register as an employer and operate PAYE. Registration should happen before the first payday and can take up to 15 working days for the reference to arrive, so start early.
You then submit a Full Payment Submission on or before every payday, even if the pay is the same GBP 1,047.50 a month every month. PAYE and NI due are payable by the 22nd of the following month if you pay electronically, or quarterly if your average monthly liability is under GBP 1,500.
For 2026/27 the figures that matter to a one director company are: employee NI at 8 per cent between GBP 12,570 and GBP 50,270 then 2 per cent above; employer NI at 15 per cent above the GBP 5,000 secondary threshold; and Employment Allowance of GBP 10,500, which a company whose only employee is a single director cannot claim. See HMRC's rates and thresholds for employers 2026 to 2027.
VAT: the GBP 90,000 threshold and how the test really works
The registration threshold is GBP 90,000 of VAT taxable turnover, and it is not measured by financial year. There are two tests. The backward look: at the end of every month, add up the last 12 months of taxable turnover, and if it exceeds GBP 90,000 you must notify HMRC within 30 days of the end of that month, with registration effective from the first day of the second month after you went over. The forward look: if you expect to exceed GBP 90,000 in the next 30 days alone, you must register immediately, effective from the date the expectation arose.
A company that crosses the threshold in the 12 months to 30 November 2026 must notify by 30 December 2026 and is registered from 1 January 2027. The deregistration threshold is GBP 88,000. Details are on HMRC's VAT thresholds page, and you can model the effect on your pricing with our VAT calculator.
Once registered you are in Making Tax Digital for VAT from day one: digital records and returns filed through compatible software, normally one month and seven days after each quarter end. The Flat Rate Scheme is available below GBP 150,000 of turnover, but most service companies fall into the 16.5 per cent limited cost trader category, which usually makes it worse than standard VAT accounting.
Self assessment: you are a director now
Being a director does not by itself require a tax return, but taking dividends almost always does. If your dividends exceed the GBP 500 dividend allowance and you have tax to pay, you must register for self assessment by 5 October following the end of the tax year, file online by 31 January, and pay by the same date.
Dividend rates rose from 6 April 2026 to 10.75 per cent for basic rate taxpayers and 35.75 per cent for higher rate taxpayers, with the additional rate unchanged at 39.35 per cent. That change applies to dividends paid in 2026/27, reported on the return due by 31 January 2028. Dividends paid in 2025/26, on the return due by 31 January 2027, still use the old 8.75 and 33.75 per cent rates. Getting these two years the wrong way round is the most common mistake we see in first year director returns.
Watch payments on account too. If your self assessment bill exceeds GBP 1,000 and less than 80 per cent of your tax was collected at source, you pay half of the bill again on 31 January and another half on 31 July. In your first dividend year that effectively means paying 150 per cent of the bill in one January.
The full first year calendar
For a company incorporated on 12 September 2025 with a 30 September accounting reference date:
| Deadline | Obligation | Body |
|---|---|---|
| Before first payday | Register as an employer and operate PAYE | HMRC |
| Within 3 months of trading | Tell HMRC the company is active | HMRC |
| 25 September 2026 | First confirmation statement (GBP 50 digital) | Companies House |
| 5 October 2026 | Register for self assessment for 2025/26 | HMRC |
| 31 January 2027 | 2025/26 tax return, balancing payment and first payment on account | HMRC |
| 12 June 2027 | First accounts (21 months from incorporation) | Companies House |
| 12 June 2027 | Corporation tax for period 1 | HMRC |
| 1 July 2027 | Corporation tax for the 19 day stub period | HMRC |
| 31 July 2027 | Second payment on account | HMRC |
| 25 September 2027 | Second confirmation statement | Companies House |
| 30 September 2027 | Both CT600 returns | HMRC |
What each missed deadline costs
Companies House late filing penalties for a private company are GBP 150 for accounts up to one month late, GBP 375 for one to three months, GBP 750 for three to six months and GBP 1,500 beyond six months, doubled if you file late two years running. They are automatic and appeals succeed only in genuinely exceptional circumstances.
A late CT600 costs GBP 100 immediately, a further GBP 100 after three months, then HMRC estimates your bill and adds 10 per cent of the unpaid tax at six months and another 10 per cent at twelve months. Three consecutive late returns push the flat penalties to GBP 500 each. Late corporation tax payment attracts interest from the day after the due date.
Missing a confirmation statement is the most serious of all: the company can be struck off the register and directors can be personally fined up to GBP 5,000. Put all of these dates in a calendar on incorporation day, and use our limited company tax calculator to work out what to set aside each month rather than discovering it nine months later.