Establish what is owed before you contact HMRC
Years of not filing do not always mean years of tax owed, so the first job is a year-by-year review rather than a panicked phone call. Genuinely nil outcomes are common in cross-border cases: you may have been non-UK resident for some of the years, so most non-UK income was outside UK scope; a double tax treaty may have given taxing rights to the other country or foreign tax credits may cover the UK liability; and for tax years up to and including 2024/25 an eligible non-domiciled person who claimed the remittance basis was not taxed on unremitted foreign income. Gather bank statements, rental accounts, dividend vouchers and your residence history for each year before anything is submitted. The 90-day clock has not started yet, so use this time. Our HMRC nudge letters and Worldwide Disclosure guide sets out the full process.
The Worldwide Disclosure Facility step by step
Where UK tax is due and any of it relates to an offshore matter, the Worldwide Disclosure Facility is HMRC's standing route. You notify HMRC through the Digital Disclosure Service, HMRC writes with a unique disclosure reference number, and the 90-day window to calculate and submit runs from that acknowledgement; an additional 90 days can be requested for complex cases. The scope depends on behaviour: broadly four years where you took reasonable care, six where careless, and up to 12 or 20 years for offshore matters and deliberate behaviour respectively. Getting that classification right is the single most valuable judgement in the process. Undisclosed UK residential rent usually fits the Let Property Campaign better, and if there is foreign rent involved our foreign rental income guide explains how the profit is computed.
What it costs, and getting back into the system
A disclosure costs the tax itself, late payment interest running daily from each original due date, and a penalty that depends on behaviour, on whether the disclosure was prompted, and on the territory category: maximums are 100% of the tax for category 1 territories, 150% for category 2 and 200% for category 3. Reasonable care means no penalty at all. A careless error in a category 1 territory carries 0% to 30% unprompted or 15% to 30% prompted. Complete, accurate disclosures are normally accepted without a full investigation, and HMRC acknowledges a completed disclosure within 15 days. Going forward, register for Self Assessment by 5 October after the end of the tax year in which new income arises; our expat Self Assessment guide covers registration, the SA109 residence pages and the £100-and-rising late filing penalties you are trying to avoid.