Why tax-free-in-India interest still belonged on your UK return
The exemption is Indian, and it stops at the Indian border. NRE-account interest is exempt in India under Section 10(4)(ii) while you are non-resident, and FCNR-account interest under Section 10(15)(iv)(fa), so the bank deducts no tax and nothing shows on an Indian return. That is where the tax-free reputation comes from, and inside India it is correct.
The UK does not recognise it. A UK resident taxed on the arising basis is taxed on worldwide income as it arises, so the NRE and FCNR interest is UK-taxable foreign savings income at your UK rates. And because India levied no tax, there is no foreign tax to credit against the UK charge, so unlike taxed Indian income it brings no relief. One caveat matters for older years: if you were historically a non-domiciled resident using the remittance basis and did not bring the interest into the UK, you may not have owed UK tax on it then. That regime was abolished from 6 April 2025, so for anyone on the arising basis the interest is now plainly UK-taxable and any past gap needs correcting.
What the Worldwide Disclosure Facility is
The Worldwide Disclosure Facility is HMRC's standard route for telling them about a UK tax liability connected to anything offshore, including foreign interest that was left off your returns. It has run since 5 September 2016 and anyone can use it, including a non-UK resident.
It works in two steps. First you notify HMRC through the Digital Disclosure Service, and they issue a disclosure reference number. Then you have 90 days from that acknowledgement to submit the full disclosure, the income year by year with the tax, interest and penalty worked out, and to pay. The reason to use it rather than wait is simple: a disclosure you volunteer is treated far more leniently than a liability HMRC uncovers from the Indian account data it already receives under the Common Reporting Standard.
How far back it goes, and the penalty
How many years are in scope, and how large the penalty is, both turn on behaviour. An innocent oversight reaches back fewer years and carries a smaller, tax-geared penalty; a deliberate and prolonged failure opens the longest assessment window, up to 20 years, and at the extreme can bring criminal exposure.
For older undisclosed years there is a sting worth knowing about. Anyone with undeclared offshore tax that was still uncorrected after the Requirement to Correct deadline of 30 September 2018 falls under the Failure to Correct regime, where the penalty starts at 200% of the tax and reduces toward a 100% floor depending on how good the disclosure is, with a further asset-based penalty of up to 10% where the tax in a year tops 25,000 pounds. So the headline is real for older years, and voluntary disclosure through the facility is exactly what brings the penalty back down. One possible mitigant is the India-UK tax-sparing credit, which can in principle credit the Indian tax that was spared on NRE interest, but it is capped at 15%, limited to about 10 years, and it is genuinely unsettled whether HMRC allows it on interest that was fully exempt, so treat it as an adviser-dependent maybe, not a certainty.
The India side, which is where we come in
The disclosure lives or dies on the numbers, and the numbers are Indian. To file it you need an accurate history of the NRE and FCNR interest you earned, year by year, for however many years are in scope, potentially a long way back. That means going to each Indian bank for the interest certificates and account statements, reconstructing the interest per financial year, and converting it to the relevant UK tax years so your UK adviser can drop it straight into the disclosure.
That reconstruction, from Indian banks, in a form a UK adviser can use, is the India-side work a practising CA does. We compile the interest history, confirm the Indian exemption basis so the position is clearly stated, and hand over a clean pack. We do not file your UK disclosure or deal with HMRC, that is your UK adviser's role. We make sure the Indian figures behind it are complete and right, because an under-stated or patchy history is what turns a clean disclosure into a reopened one.