1. Recover what was actually filed
Obtain the submitted return, supplementary pages, computation and filing acknowledgement. A draft is not sufficient. Create a schedule comparing each original figure with the proposed correction and retain the supporting documents.
2. Establish the right year and treatment
For omitted income, assemble the contract, invoice, bank entry and relevant correspondence. A bank receipt alone does not settle the tax year or whether an amount is employment, trading, investment or other income. Review the applicable rules before entering it.
For overseas items, identify source, currency, foreign tax and the period it covers. Keep conversion workings and assess credit relief separately. Do not assume all foreign deductions are creditable against UK tax.
3. Check the amendment window
HMRC normally allows changes within 12 months of the Self Assessment deadline. For 2024/25, the usual amendment deadline is 31 January 2027. Check unusual filing circumstances and any enquiry before relying on that date. Commercial-software returns may need correction through the software provider.
4. Treat older years separately
Outside the amendment window, HMRC directs taxpayers to write to it. For omitted income, explain the year, reason and estimated underpayment. Overpayment relief has separate conditions and a general four-year time limit from the end of the relevant tax year. A refund is not automatic merely because a figure was wrong.
5. Reconcile the revised bill
Check the revised liability against tax already paid and any payments on account. Keep submission evidence and review the updated statement, payment deadline and interest. A correction does not itself establish that no penalty can arise.
Arrange a defined review
Send a summary of the error, affected years, filing method and any HMRC contact. We agree the scope and fee after reviewing the information. Personal tax services start from £400; corrections, reconstruction and disclosures are scoped according to the work required.
UA Tax serves London and clients across the UK. Get in touch to request a review. Detailed records should follow through the secure route we arrange. Any explanatory letter must reflect verified evidence and cannot guarantee a third party’s decision.
For advice on your own circumstances, see our tax return corrections service and agree the scope before acting.
Official sources and further reading
These primary sources support the framework above. Check the current version before acting because tax law and HMRC guidance can change.