Self Assessment deadline: 31 January 2027 for tradespeople

Payments on account, on 31 January and 31 July

HMRC's payments on account page (opens in a new tab) says these are payments towards the next tax bill, including Class 4 National Insurance if you are self-employed. Each one is half the tax you owed last year. They are due by midnight on 31 January and midnight on 31 July.

HMRC says you must make both payments unless either of these is true: the tax you owed last year was less than £1,000, or last year you paid more than 80% of the tax you owed outside Self Assessment, for example through a tax code, or because a bank had already deducted interest on savings. The statement or the online account shows the amounts if they apply.

If the estimate those payments were based on was low, there can still be tax to pay on top. HMRC calls that a balancing payment: the total tax, minus the payments on account already made. It is due by midnight on 31 January the following year, and it can include capital gains or student loans where those apply.

If you made payments on account last year, 31 January is both the balancing payment still owed and the first payment on account towards the next bill. The second is 31 July. For this return, 31 January 2027 can hold the 2025 to 2026 balancing payment and the first payment on account for 2026 to 2027, with the second on 31 July 2027. On a first return, with no payments on account last year, January is the full tax for the year plus that first payment on account.

HMRC lets you ask for lower payments on account, online or on form SA303, if the next bill will be smaller. If you reduce them and the bill is higher, you are charged interest on the difference.

The 30 December 2026 option to pay through a tax code

The deadlines page says that if you want to pay the Self Assessment bill through your tax code, you must submit the online return by 11:59pm on 30 December 2026. Miss that, and you pay another way. The tax-code page (opens in a new tab) sets the conditions. All of them have to apply:

• you owe less than £3,000 on the bill, and you cannot make a part payment to get under that line
• you already pay tax through PAYE, for example as an employee or because you get a company pension
• you submitted a paper return by 31 October or an online return by 30 December

If those are met, HMRC collects the bill through the tax code automatically, unless you asked them not to on the return. It comes off salary or pension in equal instalments over 12 months.

HMRC will not do this if there is not enough PAYE income, if you would pay more than 50% of that income in tax, or if you would pay more than twice as much tax as usual. A part payment to get under £3,000 does not open the door. Class 2 National Insurance cannot go through the code unless it has been due since before 6 April 2015.

A draft that says "put it through the code" because the bill looks small has skipped the PAYE test and the £3,000 test. The allowable expenses guide is about what HMRC allows you to deduct before that calculation exists. It does not move 30 December.

Turn these HMRC dates into a checklist for the 2025 to 2026 tax year. UK English. Use only the dates I type. Do not add a date. Do not say I can pay through a tax code. Do not say I must make payments on account.

Paper return must be received by:
Online return must be submitted by:
Tax due by:
Online filing date if I want the bill collected through a tax code:
First payment on account date, or "not on my statement":
Second payment on account date, or "not on my statement":

Read the checklist against the deadlines page. January is the payment and the online filing date. December is only the tax-code route, and only where the conditions are met.

What the January bill is actually made of

The bill is the tax on the profit after allowable expenses, plus Class 4 National Insurance where it applies, minus what has already been paid. HMRC's CIS page (opens in a new tab) says you record the pay before deductions as income, and the deductions as CIS deductions. HMRC takes those deductions off the tax. Anything still owed is paid by 31 January after the tax year. A refund, if one is due, is paid back by HMRC. The rate is explained in the CIS guide. It is not VAT. That split is in the VAT reverse charge guide.

Do not paste your Unique Taxpayer Reference, your National Insurance number, or a contractor's bank details into a chat. The dates, and the totals you have already taken from the calculation, are enough.

Explain this Self Assessment calculation in plain English. UK English. Use only the figures I type. Do not change a number. Do not tell me to reduce a payment on account. If a figure is missing, write MISSING.

Tax year:
Tax and Class 4 National Insurance for the year:
Payments on account already made:
CIS deductions on the statements:
Balancing payment the calculation shows:
First payment on account the calculation shows for the next year:
Total the calculation says is due on 31 January:

If your own sum does not match the calculation, use the calculation. A second draft will not file the return.