What to Do in the First 48 Hours After an HMRC Letter Arrives

Start by reading the letter slowly, more than once, and identifying three things: which tax and period it relates to, what specifically has been requested, and the exact deadline stated. It's easy to misread a deadline under stress, so it's worth double-checking the actual date rather than working from memory after a first skim.

It also helps to note down, in your own words, what you think the letter is asking for before you do anything else. A one-sentence summary such as 'HMRC wants to see bank statements for my business account covering the 2024/25 tax year' forces you to confirm you've actually understood the request correctly, rather than skimming past a detail that later turns out to matter.

Breaking the first two days into smaller windows makes the task feel far more manageable than treating it as one large, undefined problem to solve immediately.

Resist the urge to call HMRC or send a reply before you've located the relevant records and had a chance to review them, since an off-the-cuff answer given under pressure can be harder to walk back than a slightly delayed but accurate one.

Certain wording in a letter should prompt faster action than the general 48-hour approach described here — anything referencing a criminal investigation, a Code of Practice 9 or 8 case, or a very short deadline measured in days rather than weeks. These situations carry higher stakes and narrower windows to get professional advice involved before you say or send anything.

If you decide to call HMRC before responding in writing, keep a written note of the call as you make it — the date, the name of the person you spoke to if given, and a summary of what was said on both sides. Phone conversations with HMRC aren't always fully documented on their end in a way that's easy to retrieve later, so your own contemporaneous note can become surprisingly important if there's ever a dispute about what was agreed or said.

By the end of the first 48 hours, you should ideally have a clear one-line summary of what's actually being asked, a note of the real deadline, and a short list of the records you'll need to pull together — which puts you in a considerably stronger position than reacting immediately without that groundwork.

Picture two people receiving the same letter asking for evidence of a specific expense claim. The first calls HMRC within the hour, gives an approximate answer from memory, and later realises the figure was slightly wrong — creating a discrepancy between what was said on the phone and what the records actually show. The second spends the first day locating the invoice, confirms the figure is correct, and replies in writing with the exact document attached.

The second approach isn't just more accurate — it's also faster overall, since it avoids the follow-up questions the first approach almost always generates once HMRC spots the mismatch between what was said and what the paperwork shows.