Your Self Assessment Checklist
Everything your accountant needs to file a quick, accurate and low-cost return. Gather the right documents once, hand over a complete pack, and the rest is done for you, with nothing chased back and forth.
- Late filing penalty
- £100
- Trading allowance
- £1,000
- Property allowance
- £1,000
The key dates, and what you sign in with
Miss a date and the penalties start automatically, whatever the tax due, so sort the dates and your sign-in details first. If this is your first return, register by 5 October after the tax year so HMRC can issue your UTR in time. Paper returns are due by 31 October, but almost everyone files online by 31 January, which is also the day the tax is due. A second payment on account, if you make them, falls on 31 July.
- Register by 5 October after the tax year if it is your first return
- 31 October for paper returns, 31 January to file online and pay the tax
- You sign in with your 10-digit UTR, your Government Gateway user ID and password, and your National Insurance number
A new UTR and Government Gateway access can take a couple of weeks to arrive by post, so register early and do not assume you can register and file on the same January day.
The income checklist
Your return must show all your taxable income for the year, not just your main job, even where tax was already taken off at source. Work down the list and gather the document beside each source that applies to you.
- Self-employment: total income and allowable expenses, from your bookkeeping or bank statements
- Employment and pensions: P60 from each job or pension held at 5 April, P45 for any job you left, P11D for taxable benefits
- Dividends, interest and rental income: vouchers, interest certificates, rent and expense records
- Other income: foreign income, trusts, capital gains and casual or side income
A P60 is the year-end summary from each job or pension you held on 5 April, a P45 covers a job you left part way through, and a P11D reports benefits like a company car. Gather one of each that applies, for every employer.
Expenses, reliefs and the charges to watch
The right reliefs cut what you owe, and a few charges can quietly increase it. Pension contributions and Gift Aid donations extend your basic-rate band, giving higher-rate taxpayers extra relief through the return, and allowable business expenses reduce self-employment profit. If your trading or rental income is small, the 1,000 pound trading allowance and the 1,000 pound property allowance can replace your actual costs.
- Pension contributions and Gift Aid: note the totals, higher-rate relief is claimed on the return
- Trading and property allowances: a separate 1,000 pounds each, claim the flat amount or actual costs, whichever is higher, never both
- Student loan: note your plan type, repayment is collected through the return
- High Income Child Benefit Charge: can apply where you or your partner receive Child Benefit and either of you has income over 60,000 pounds
The Child Benefit charge applies from 60,000 pounds and reaches a full clawback at 80,000 pounds, so flag it early if that could be you.
Penalties for filing late, then your handover pack
The penalties stack up fast and apply even if you owe no tax, so gather your pack in good time. You are charged a 100 pound fixed penalty the day the return is late, then 10 pounds a day up to 900 pounds once you are over 3 months late, then 5% of the tax due, or 300 pounds if greater, at both 6 months and 12 months. Paying the tax late is a separate charge, with further 5% penalties at 30 days, 6 months and 12 months, and interest running daily until you pay.
- The day it is late: 100 pounds, even if you owe no tax
- Over 3 months late: 10 pounds a day, up to 900 pounds
- Over 6 and over 12 months late: 5% of the tax due, or 300 pounds if greater, each time
If your last bill was over 1,000 pounds you usually make two payments on account towards next year, each half of last year tax, due 31 January and 31 July, so budget for both.
Common questions
What are the Self Assessment deadlines?
Register by 5 October after the tax year if it is your first return. Paper returns are due by 31 October, and online returns by 31 January, which is also when the tax is due. If you make payments on account, the second one falls on 31 July. A new UTR and Government Gateway access can take a couple of weeks to arrive by post, so do not leave registering to January.
What documents do I need for my tax return?
Your sign-in details first: your 10-digit UTR, your Government Gateway user ID and password, and your National Insurance number. Then every source of income, with the record behind it: P60, P45 and P11D for employment and benefits, dividend vouchers, interest certificates, rental records, pension figures and any other income. Finally your reliefs and charges: expense totals, pension and Gift Aid figures, your student loan plan type, and any Child Benefit charge.
What are the penalties for filing late?
You are charged 100 pounds the day the return is late, even with no tax to pay, then 10 pounds a day up to 900 pounds once you are over 3 months late, then 5% of the tax due, or 300 pounds if greater, at 6 months and again at 12 months. Paying late adds separate 5% charges at 30 days, 6 months and 12 months, with daily interest. Gather a complete pack in good time and none of this can touch you.
Print this part and work through it
Everything below is built to keep. Print it, fill it in, and take it to any conversation, including ours.
Your Self Assessment document checklist
Tick each item that applies to you, gather the document beside it, and hand the complete pack to your accountant ready to file.
- Your 10-digit UTR, Government Gateway user ID and password, and National Insurance number
- P60 from each job or pension held at 5 April, and P45 for any job you left
- P11D for a company car or other benefits
- Self-employment income and expense totals
- Dividend vouchers, interest certificates, and rental income and cost records
- Pension and any other income figures
- Allowable expense totals by category, pension contributions and Gift Aid donation total
- Decide on the 1,000 pound trading allowance and the 1,000 pound property allowance
- Note your student loan plan type, and flag the Child Benefit charge if income is over 60,000 pounds
- Check whether you owe payments on account, diarise 31 January to file and pay, and keep records for at least 5 years
When every relevant box is ticked, send the pack to your accountant in one go. A complete handover means no back-and-forth, the lowest fee, and a return filed well before the deadline.
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For guidance only — this factsheet does not constitute professional advice and is not a substitute for advice based on your specific circumstances. Whilst every care has been taken in its preparation, it may contain errors for which we cannot be responsible. Figures are for the 2026/27UK tax year (England, Wales & Northern Ireland) and may change. Last reviewed 4 May 2026.