What decides where the fee lands
A repeat, stable year sits at the lower end of the range: one straightforward UK income source, a clear-cut non-resident position and a return much like last year's. Years of change push the fee towards the complex end: a first year abroad where a split-year claim must be decided, a UK property sale with its own 60-day reporting deadline, multiple UK income sources, or a double tax treaty claim. Whatever the scope, a reputable adviser agrees a fixed fee in writing before any work starts, so the price cannot drift.
The trap: comparing against a free option that does not exist
Many expats assume the alternative is filing free on HMRC's website. GOV.UK is explicit that non-residents cannot use HMRC's online services to report their income, because the free service does not support the SA109 residence pages where non-resident status, split-year treatment, the personal allowance and treaty claims are made. DIY therefore means a paper return that HMRC must receive by 31 October, or SA109-capable commercial software filed by 31 January. The cash saving is real, but nobody reviews a DIY return for missed reliefs: HMRC will not add them, and one missed split-year claim or allowance can cost several times a typical fee.
What to do
Match the route to your year. If you were clearly non-resident throughout, have one simple income source and are repeating a correctly filed year, DIY through SA109-capable software is a reasonable saving. If anything changed, get a fixed quote in writing and weigh it against the cost of a missed claim: up to £2,514 a year for the personal allowance alone, plus penalties from £100 to at least £1,600 if a deadline slips. The full comparison, including when DIY is fine, is in our guide to DIY Self Assessment vs using an accountant when you live abroad.