Why HMRC's free online service is closed to you
Almost every return filed from abroad needs the SA109, the supplementary pages headed 'Residence and foreign income and gains (FIG) regime etc' from 2025/26, where non-residence, split-year treatment, treaty claims and FIG claims are declared. HMRC's free online service has never supported these pages, and GOV.UK is explicit that if you are non-resident you cannot use HMRC's online services to report your income. This is a long-standing design limitation, not a temporary outage, and HMRC has published no timetable for changing it. The full background is in why the SA109 cannot be filed online.
The 31 October paper trap
Because the free service is closed, the default route is a paper return, and paper has a much earlier deadline: HMRC must receive it by 11:59pm on 31 October 2026 for the 2025/26 tax year, not the 31 January date most filers assume. Miss that and a £100 penalty follows automatically, even if you owe no tax, with daily £10 penalties from three months late. If 31 October has already passed, do not post a paper return: file online through software or an agent by 31 January 2027 instead, and no late filing penalty arises.
How to actually file online
Two online routes preserve the 31 January deadline. You can buy commercial software from HMRC's list of recognised Self Assessment suppliers, checking before you pay that it includes the SA109, which GOV.UK notes may appear as a 'residence' or 'remittance basis' section. Or you can use an agent, who files through professional software with the SA109 included as standard; the added value is the judgement behind the boxes, such as confirming your Statutory Residence Test outcome, picking the right split-year case and checking any treaty or FIG claim. See expat Self Assessment for what a non-resident return involves end to end. Whichever route you choose, any tax due for 2025/26 must still be paid by 31 January 2027.