Mistakes in the claim itself
The FIG regime punishes vagueness. HMRC's Residence and FIG Regime Manual at RFIG42100 states that the amount of relief claimed must be quantified in the return on a source by source basis, and that a claim which quantifies nothing at all is invalid. An invalid claim is the worst outcome: your dates may qualify perfectly, but with no effective claim you are a UK resident taxed on worldwide income and gains. Getting a number wrong is more forgiving. The claim survives, but relief attaches only to the amounts you declared and claimed, so anything omitted stays taxable until you fix it. The repair route is an amendment within the claim's time limits: under RFIG42300 a 2025/26 claim can be made, amended or withdrawn up to 31 January 2028, with a modest extension where HMRC issued the notice to file after 31 October. There is also a quieter failure mode: claiming when the arithmetic never worked, because the claim costs you the personal allowance and CGT annual exempt amount. Our guide to common FIG mistakes covers the patterns we see.
What HMRC can charge
Miss the deadline and the standard Self Assessment penalties apply: £100 the day after the deadline, £10 a day after 3 months up to £900, then the greater of 5% of the tax due or £300 at 6 months and again at 12 months, plus late payment penalties of 5% of the unpaid tax at 30 days, 6 months and 12 months, with interest on top. Inaccuracies are penalised as a percentage of the extra tax: 0% to 30% for failing to take reasonable care, 20% to 70% for a deliberate error and 30% to 100% where the error is deliberate and concealed. The sting for FIG claimants is that foreign income and gains are offshore matters, and HMRC's factsheet CC/FS17 applies higher ranges by territory category: maximum penalties of 100% of the tax for category 1 territories, 150% for category 2 and 200% for category 3. The same factsheet logic cuts the other way too: a careless error, disclosed unprompted and supported by good records, sits at the bottom of the range, and HMRC treats keeping adequate records and asking about uncertainty as the hallmark of reasonable care.
Fixing past years
If a problem predates the current amendment window, the route back is disclosure rather than silence. HMRC's Worldwide Disclosure Facility exists for exactly this: you notify HMRC of a UK tax liability relating to an offshore issue, then have 90 days to calculate and disclose the tax, interest and penalties. Coming forward unprompted materially reduces the penalty position compared with waiting for HMRC to write first, and HMRC's guidance warns that higher penalties apply where someone delays correcting the position, so waiting rarely ends well. Our guide to HMRC nudge letters and worldwide disclosure explains the process.
The cheap insurance: file it properly once
Every outcome above is priced off the same thing: whether the return was accurate and the claim quantified. That is a solvable problem. Horizon UK Tax Solutions is founder-led by a Chartered Tax Adviser with over 10 years experience, including 7 at a Big Four firm, and FIG returns are exactly the returns we specialise in. We prepare and file the full SA109 claim for a fixed fee agreed upfront, with non-resident and expat returns from £550 and complex returns from £750, which is a rounding error next to a single offshore penalty. Book a free 30-minute clarity call or see our non-dom and residency services.