The nudge letter is one of HMRC's soft-power tools, used for years to prompt voluntary disclosure from a broad group of taxpayers without the cost or formality of a full enquiry. 

But recently, the target has changed. HMRC has begun writing directly to a small, identified cohort of UK-connected billionaires, inviting them to share details of their trusts, assets and property voluntarily, with some also asked in for a meeting. That shift in audience, from mass-market nudge to bespoke outreach for a few hundred individuals is worth examining.

Compliance or Information Gathering Exercise?

HMRC does not currently have a reliable picture of how much tax billionaires in the UK pay. A parliamentary committee said as much last year, and recommended that HMRC start treating the ultra-wealthy as a distinct segment rather than folding them into the broader "wealthy" population it already monitors. If the nudge letters are a direct response to this information gap, then these letters are not really about enforcement. They are HMRC building the dataset it should arguably have had already, using the taxpayer's own disclosure rather than its own investigative resources to do it.

It is also widely reported that the number of high-profile wealthy individuals restructuring their affairs or leaving the UK has accelerated sharply since the old non-dom regime was withdrawn. A letter asking a globally mobile billionaire to set out UK trusts, assets and property is also, functionally, a way of mapping who still has ties to the UK and how easily those ties could be severed.

The real danger isn't disclosure. It's inconsistency.

Most of the commentary on these letters frames the decision as binary: disclose, or don't. That misses where the actual risk sits. HMRC rarely needs taxpayer input to open a formal enquiry. It needs a discrepancy - a fact stated now that does not sit comfortably with something said, or not said, in a return, a previous enquiry, a disclosure facility submission, or information obtained through automatic exchange of information from another jurisdiction years ago.

A voluntary letter response is not assessed in isolation. It lands in a file that already contains years of history: prior correspondence, prior positions taken by advisers who may no longer act, residence and domicile claims made in earlier tax years, and third-party data HMRC has held for some time but never acted on. The moment a new answer does not quite match that existing record - even where the mismatch is innocent, a difference of emphasis, or simply the product of a structure evolving over time - HMRC has what it needs to open a discovery assessment. Discovery does not always require fraud, dishonesty or even carelessness. Where the matter has an offshore element, subject to certain restrictions, it only requires HMRC to become aware of something it considers it did not previously know, and a letter that volunteers a fact in a new frame can be exactly what manufactures that awareness.

This is why responding "a little, carefully" is not actually a safer middle ground than responding fully or not at all, if you do not check what the existing record actually says before answering.

How to approach a nudge letter

The only way to answer one of these letters safely is to first establish, with precision, two things: 

1. What has already been told to HMRC  across all historic filings, disclosures, enquiry correspondence and adviser submissions; and 
2. What HMRC is independently likely to hold through automatic exchange of information, land and company registries, and increasingly, its own AI-assisted data matching. 

Only once both pictures exist side by side is it possible to see where a new answer might create a gap, and to decide, deliberately, how to close it or explain it before HMRC finds it unexplained.

Treating the letter as a standalone, low-stakes request because it carries no formal power behind it is the wrong instinct. A quick, well-meaning response drafted without that reconstruction exercise is how an ordinary voluntary enquiry becomes a multi-year dispute. The work that actually protects a client here is not clever drafting of the letter back to HMRC. It is the unglamorous exercise of mapping the client's full disclosure history and HMRC's likely data position before a single word is sent, because by the time a discrepancy surfaces in a formal enquiry, the conversation is no longer about the facts. It is about why the facts changed.