8 August 2026

SA302 Adjustment Income: Why HMRC's Figures Differ From Yours

If your SA302 shows a different income figure to what you submitted on your Self Assessment return, you're not alone. HMRC applies adjustments that can catch freelancers and sole traders off guard. Here's what adjustment income means, why it appears, and exactly how to challenge it.

Drafted by EasyTax's automated research pipeline from HMRC guidance and UK legislation, published by Finance Panda Limited on 8 August 2026.

This article predates our editorial review gate and has not been individually checked by a person. We are working back through the archive. Treat the figures and dates here as a starting point and verify anything you are about to act on.

How we write and check these articles

What Is Adjustment Income on an SA302?

Your SA302 is HMRC's official tax calculation document, often requested by mortgage lenders and banks as proof of income. It's generated from your Self Assessment return, but it doesn't always mirror the figures you submitted. One common source of confusion is something HMRC labels as adjustment income — a catch-all term for modifications HMRC makes to your declared figures when calculating your final tax liability.

These adjustments can increase or decrease your taxable income, and if you're not expecting them, they can cause real problems — particularly when a lender questions why your SA302 doesn't match your tax return.

Common Reasons HMRC Adjusts Your Income

Marriage Allowance transfers: If you or your spouse transferred part of your Personal Allowance, this affects the SA302 income calculation.
Gift Aid donations: HMRC extends your basic rate band to account for Gift Aid, which can change how much income falls into higher rate bands.
Pension contributions: Personal pension contributions paid without relief at source can trigger an adjustment to your taxable income figure.
Student loan repayments: These are calculated on an adjusted income basis and can appear as a separate line affecting the overall figure.
High Income Child Benefit Charge: If your adjusted net income exceeds £60,000 (as of the 2024/25 tax year), HMRC adds this charge, which feeds into the SA302 total.
Underpayment restrictions: If HMRC is collecting an earlier underpayment through your tax code, this can appear as an adjustment on your SA302.

Adjusted Net Income vs Total Income

It's worth understanding the distinction HMRC draws between total income and adjusted net income. Total income is your gross income from all sources before reliefs. Adjusted net income is that figure after deducting things like pension contributions, Gift Aid payments, and trading losses. Many of the figures on your SA302 are based on adjusted net income, which is why the number rarely matches the turnover or profit you declared on your SA100.

How to Check Whether the Adjustment Is Correct

Start by logging into your HMRC online account at gov.uk/personal-tax-account and downloading your SA302 for the relevant tax year. Then compare it line by line against your submitted return. HMRC also provides a tax calculation breakdown — look for the section titled Income Tax Calculation within your online account.

If you filed through commercial software or through an accountant, request a copy of the computation they submitted. Any discrepancy between that computation and your SA302 is worth investigating immediately.

How to Challenge an Incorrect SA302

If you believe HMRC has applied an incorrect adjustment, you have a clear route to challenge it:

Amend your return: If your Self Assessment return contains an error, you can amend it online within 12 months of the 31 January filing deadline. For the 2024/25 return, you have until 31 January 2027.
Contact HMRC directly: Call the Self Assessment helpline on 0300 200 3310 and ask for a manual review of your tax calculation. Have your UTR number ready.
Submit a formal appeal: If you disagree with a tax assessment, you can appeal within 30 days using form SA370 or by writing to HMRC. State clearly which figure you dispute and why.
Request a statutory review: If HMRC upholds its position, you can ask for an independent review before escalating to the First-tier Tax Tribunal.

A Practical Note for Mortgage Applications

If a lender is querying your SA302, ask your accountant or tax adviser to provide a covering letter explaining any adjustments. Most mortgage underwriters will accept a clear written explanation alongside the SA302, particularly if the adjustment relates to pension relief or Gift Aid rather than a disputed liability.

Getting your SA302 figures right matters beyond tax — it directly affects your ability to borrow. Don't assume HMRC's calculation is always correct, and don't leave discrepancies unchallenged.

Keep reading

Cash Basis & MTD ITSA: Invoice Date vs Payment Date Explained

Under Making Tax Digital for Income Tax Self Assessment, cash basis sole traders must record income when money actually lands in their account — not when they raise an invoice. Getting this wrong could mean misreporting quarterly figures to HMRC. Here's exactly what you need to know.

Basis Periods for New Sole Traders: Your First Tax Bill Explained

Starting out as a sole trader means navigating HMRC's rules on basis periods — the time frame used to calculate which profits are taxed and when. Under the new tax year basis rules that took full effect from 2024/25, things work differently to how they did before. Here is exactly what you need to know about your first year's tax bill.

Cash Basis vs Accruals: When Does a Late Invoice Count as Income?

If a client pays your invoice three months late, do you declare that income in the tax year you raised the invoice or the year you received the money? The answer depends on which accounting method you use — and getting it wrong can land you with an unexpected tax bill. Here is exactly how the rules work for sole traders and freelancers under Self Assessment.

This article is for general information only and does not constitute tax advice. For your specific situation, consult a qualified accountant.

← More Tax Tips