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Self Assessment · First returnLive — Available now

Your first Self Assessment tax return, step by step

A first return starts with telling HMRC. Register by 5 October after the tax year, get your UTR and activation code, file online by 31 January and pay the same day. Your first bill can include a first payment on account on top, so it is usually bigger than the tax for the year.

HMRC-recognised · you register with HMRC, then bring your UTR · pay only when you file
What we fill in first
Box 4National Insurance number
Box 5Date your business started
Box 10.1Trading income allowance
BOXES FIRST-TIMERS MEET

The boxes a first return always has.

Which pages you need depends on why you are filing; these are the ones first-timers meet most. Your job is the SA102, a new business the SA103S, and personal details are on the SA100 itself.

SA100 · Box 4

National Insurance number

Part of the personal details every return starts with, alongside your date of birth. HMRC matches the return to you by these and your UTR.

SA102 · Box 1–2

Pay and tax taken off

If you are also employed, your job is its own page: pay and PAYE tax per employer, from the P60 or P45.

SA103S · Box 5

Date business started

For a business that began during the year. Turnover and expenses only cover the months you traded.

SA103S · Box 8

Opt out of cash basis

Cash basis — you count money when it arrives and leaves — is the standard method. This box is only ticked if you choose traditional accounting instead.

Source: Cash basis — gov.uk
FIRST-RETURN CHECKLIST

What to have ready, and where first returns stall.

Registering and filing are two separate steps with two separate deadlines. Most first-return delays come from the first, not the second.

Have ready

  • Your UTR. Registering online puts it in your personal tax account within 72 hours. By post it usually takes 15 working days, or 21 if you are abroad.
  • An activation code, if you did not register online. It arrives by post, usually within 7 working days (21 abroad), and you need it to activate the account before you can file online.
  • Your records. Bank statements, receipts and invoices. You do not send them to HMRC with the return, but you must keep them to show if asked.
  • Pay and tax figures. P60 or P45 for any job in the year, plus statements for any interest, dividends or rent.

Where first returns stall

  • Telling HMRC late. If you register after 5 October, HMRC sends a letter or email with a later deadline, three months from its date. The tax is still due on 31 January, and a failure to notify penalty can follow if it is not.
  • An old account that was never used. If you registered before but did not need to file last year, you may have to reactivate the account first. Filing without doing so can delay the return.
  • Missing the paper deadline. A paper return must reach HMRC by 31 October. Online returns have until 31 January.
  • A bigger first bill than expected. The first bill can include a first payment on account for the next year on top of this year's tax. Set money aside for both.
WHAT YOU GET

Everything this return files, keeps and tells you.

Files for you

Sent to HMRC, with a receipt you keep.

  • SA100 with the pages your income needs

Keeps for you

Your records in one place for the next one.

  • The bank feed and books behind every box
  • Your SA302 calculation

Tells you

What January will cost, before it arrives.

  • Your estimated bill before you file
  • Whether a payment on account applies
THREE THINGS PEOPLE GET WRONG

First Self Assessment returns — the small print that costs money.

No sign-up — try it right here

See your payments on account — no sign-up.

Enter your tax bill and get a labelled schedule of what falls due on 31 January and 31 July.

Fix the figures above to see an estimate.

Estimate only — not tax advice. Figures use published HMRC rates and thresholds for the selected tax year; your actual bill depends on your full return.

An estimate from the figures you enter — HMRC's statement after you file is what you pay from.

PRICING

One fee per return. No subscription.

A first return is priced like any other: by the pages it needs.

50% off until 14 January 2027
Simple
One supplementary page
£29£59/ return

A job (SA102) plus at most one other page — a small side business, say.

Start a return
Complete
Every income type
£65£129/ return

A new business with no job, or three or more pages — every supplementary page included.

Start a return

A first return, three ways.

RowHMRC onlineAn accountantac-co
£/return£0£150–£400 [Sleek — accountant fees for Self Assessment, UK, 2026-09-13]£29–£65
Registers you with HMRCYes — you do itOften, if you askNo — register on gov.uk, then bring your UTR
Drafts figures from your bank feedNoIf you send themYes

Accountant fee dated 2026-09-13 — check their own quote.

ANSWERS

Ready when you are.

How do I register for Self Assessment and how long does it take?

Register on gov.uk by 5 October after the tax year if you need a return and have not filed before. Online, your UTR appears in your personal tax account within 72 hours. By post it usually takes 15 working days, or 21 if you are abroad, and the activation code arrives in about 7 working days. ac-co starts once you have your UTR.

When is my first Self Assessment deadline?

If you registered by 5 October, an online return is due by 31 January after the tax year and a paper return by 31 October. If you registered later, HMRC confirms your filing deadline by letter or email, three months from its date. Either way, the tax itself is due by 31 January.

What records do I need for my first return?

Bank statements, receipts and invoices for everything you earned and claim. You do not send them to HMRC, but you must keep them to prove your figures if asked. Add P60 or P45 figures for any job, and statements for interest, dividends or rent. ac-co reads your bank feed to draft the figures.

Why is my first Self Assessment bill bigger than I expected?

Because it can include a first payment on account for the following year, equal to half this year's tax, on top of the tax itself. gov.uk's example turns a £3,000 bill into £4,500 on 31 January, with a second £1,500 on 31 July. Payments on account are skipped where last year's bill was under £1,000.

How much does a first return cost?

Our fee is per return, with no subscription. The Simple tier (£29) is for a return with an employment page plus at most one other supplementary page; any other return is Complete (£65). The tier is set by the pages on your filed return.

Sources

Rules and rates on this page were checked against these gov.uk pages on 12 October 2026. Tax rules change; check the page itself for the tax year you are filing.

GUIDES & ARTICLES

Read before you file.

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Registered? Bring your UTR and file.

Connect your bank, add your pay and records, review the draft, file when you're ready.