HMRC have got it wrong and the clock is ticking.

HMRC have sent a decision or penalty that's plain wrong and there's a deadline ticking. Give the decision, your NI number, the HMRC reference and your grounds. You get a formal letter requesting a statutory review under Section 49A TMA 1970: grounds stated clearly, supporting evidence referenced, and confirmation requested. Properly worded, not pleading.

Write a formal letter to HMRC disputing [describe the decision or penalty]. My National Insurance number is [NI number] and the reference on the HMRC letter is [HMRC reference]. The decision is wrong because [state my grounds]. I am requesting a statutory review under Section 49A TMA 1970. The letter should: state the grounds clearly, reference any supporting evidence I will enclose [list documents], request confirmation of receipt within 7 days, and note the 30-day appeal window. Tone: precise and respectful.