What Happens After Filing Your Tax Return

Immediate Confirmation

When you file your return online, HMRC immediately calculates your tax and shows you the result. You’ll receive:^[1]

A submission confirmation with a unique reference number
Your SA302 tax calculation — a summary showing total income, tax due, National Insurance, and any student loan repayments

You can view and download your SA302 from your HMRC online account at any time. Some mortgage lenders accept the SA302 as proof of income.

Understanding Your SA302

Your tax calculation breaks down:^[1]

Total income from all sources (employment, self-employment, property, savings, dividends)
Personal Allowance and any other deductions
Income Tax at each rate (basic, higher, additional)
National Insurance (Class 2 and Class 4 if self-employed)
Student loan repayments (if applicable)
Tax already paid through PAYE or other deductions
Amount owed (or refund due)

Paying Your Bill

If you owe tax, you must pay by 31 January following the end of the tax year. There are several payment methods:^[2]

Online banking or Faster Payments (same or next day)
Debit card through HMRC online (immediate)
Direct Debit (3 working days to set up)
Bank transfer (3 working days)
At your bank or building society (3 working days)

Always use your UTR as the payment reference so HMRC can match it to your account.

If You’ve Overpaid

If your calculation shows you’ve overpaid (for example, through PAYE deductions or payments on account), you have two options:^[4]

Claim a refund — HMRC will pay you by bank transfer or cheque
Leave it on account — the overpayment is offset against your next tax bill

Payments on Account

If your tax bill is over £1,000 and less than 80% of it was collected at source (e.g. through PAYE), HMRC will require payments on account for the following year. These are two advance payments:^[3]

First payment: 31 January (due at the same time as your current year’s bill)
Second payment: 31 July

Each payment is 50% of the previous year’s bill. Any difference is settled in a balancing payment the following January.

Record Keeping

After filing, keep all your records for at least 5 years after the 31 January deadline. For example, records for 2025/26 (deadline 31 January 2027) should be kept until at least 31 January 2032.^[1]

HMRC Enquiry Window

HMRC has 12 months from the date you filed to open an enquiry into your return. During this window, they may ask you to explain or provide evidence for figures on your return. After 12 months, they can only go back into your return if they discover an error.^[1]

Frequently Asked Questions

What happens after I submit my Self Assessment return?

HMRC immediately calculates your tax and shows you the result, including a submission confirmation with a unique reference number and your SA302 tax calculation showing total income, tax due, and any refund.

How long do I need to keep tax records after filing?

Keep all records for at least 5 years after the 31 January filing deadline. For example, records for 2025/26 (deadline 31 January 2027) should be kept until at least 31 January 2032.

Can HMRC investigate my return after I file?

Yes. HMRC has 12 months from the date you filed to open an enquiry into your return. After that period, they can only revisit your return if they discover a specific error.

What is an SA302 and why do I need it?

The SA302 is your tax calculation summary showing total income from all sources, deductions, tax at each rate, NI, and the amount owed or refunded. It is accepted by many mortgage lenders as proof of income.

Sources

Self Assessment tax returns — GOV.UK
Pay your Self Assessment tax bill — GOV.UK
Self Assessment: payments on account — GOV.UK
Claim a tax refund — GOV.UK
Contact HMRC — GOV.UK

What Happens After You File Your Tax Return