Claim personal allowances and tax refunds if you live abroad (R43).
UK non-residents can use form R43 to claim personal allowances and tax refunds on UK income for the current tax year or the previous four tax years. This process does not apply to individuals who are already required to complete a Self Assessment tax return. Claims can be submitted online or by post using the R43 form available on the GOV.UK website.
Source: https://www.gov.uk/guidance/claim-personal-allowances-and-tax-refunds-if-you-live-abroad. Summarised automatically from the official source — general information, not advice.