Two further constraints apply. HMRC must issue the assessment within one year of having enough evidence to make it, where the period assessed is more than two years old. And while HMRC's information powers are not formally time-limited, the tribunal has held that HMRC must show a plausible case before compelling records older than four years.
- Applying the six-year "careless" rule to VAT. That's the rule for Income Tax and Corporation Tax, not VAT. The VAT regime is binary: four years for everything short of deliberate behaviour, twenty years if HMRC can show the inaccuracy was deliberate. Many advisers familiar with direct tax get this wrong.
- Forgetting the one-year evidence rule. Once HMRC has enough information to calculate an assessment, the clock starts. If the period being assessed is more than two years old, HMRC must issue within one year. A late assessment on this point can be invalidated, even when the underlying VAT is not in dispute.
- Confusing the assessment window with the information notice window. Schedule 36 of the Finance Act 2008 has no effective time limit, so HMRC can in theory request records of any age. But the tribunal will only enforce notices going beyond four years if HMRC shows a plausible case for doing so.
- Treating "failure to notify" as ordinary careless. A failure to register for VAT when liable carries the twenty-year window automatically, whether or not the failure was deliberate. This catches businesses that crossed the threshold years ago without realising and assume only four years are exposed.
- Volunteering records well beyond the period under check. Cooperation matters, but producing eight years of records when HMRC has asked for four can expand the scope of the check and bring earlier periods within reach. Limit production to what the notice requires unless there is a strategic reason to go further.
The four-year rule: the standard VAT assessment window
The starting point is the VAT Act 1994, section 77. HMRC can generally raise an assessment up to four years from the end of the VAT accounting period in which the error occurred. Note the anchor: it is the accounting period, not the calendar year. A quarterly return for the period ending 31 March 2022 falls within the four-year window until 31 March 2026.
The four-year rule applies regardless of behaviour for everything short of deliberate. That includes ordinary mistakes, oversight, and what HMRC would call "careless" errors. This is where VAT differs materially from direct tax. For Income Tax, Corporation Tax, and Capital Gains Tax, careless behaviour extends the window to six years. For VAT, there is no equivalent six-year tier: the regime is binary, four or twenty.
In practice, this means a business under a VAT compliance check should expect HMRC to look at the last four years as a default. Anything older is presumptively out of time, unless HMRC is alleging deliberate behaviour or failure to notify.
The twenty-year rule: deliberate behaviour and failure to notify
Two situations extend the window to twenty years (section 77 of the VAT Act 1994):
- Deliberate inaccuracy in a return or other document. HMRC's published definition is a person who knowingly gives HMRC an inaccurate document. Burden of proof rests on HMRC, not on the taxpayer. Allegation alone is insufficient; the tribunal will look for evidence of conscious intent to mislead, not merely careless or aggressive accounting.
- Failure to notify a liability to register for VAT. This is automatic: the twenty-year window applies whether or not the failure was deliberate. A business that crossed the registration threshold years ago without realising is exposed to assessment for the entire period of unregistered trading, not just the most recent four years.
The distinction between careless and deliberate is one of the most consequential factual questions in any VAT investigation. Tribunals regularly scrutinise HMRC's behaviour allegations because they directly affect both time limits and penalty exposure. Cases like Hegarty [2018] UKFTT 774 (TC), drawing on the older Brannigan [2006] EWHC 885 (Admin), confirm that HMRC must show an arguable case for the deliberate characterisation before it can compel records or assess for periods beyond four years.
The one-year "evidence of facts" rule
This is the rule most often overlooked, and the one that most often invalidates a late assessment. Under section 73(6) of the VAT Act 1994, where HMRC raises an assessment more than two years after the end of the relevant VAT period, it must do so within one year of obtaining evidence of facts sufficient to justify the assessment.
The clock starts when HMRC has enough information to calculate the assessment on a best-judgement basis, not when HMRC chooses to act on it. Tribunals have heard a steady stream of cases on when that clock starts and stops. The recent Upper Tribunal decision in Nottingham Forest Football Club v HMRC [2024] UKUT 145 (TCC) confirmed that the burden of demonstrating which records HMRC actually used to make the assessment rests with the taxpayer, which sets a meaningful evidential bar.
The practical implication is that every email, document production, and meeting note matters. If you can show HMRC had the evidence to assess by a particular date, and HMRC issued the assessment more than a year later, the assessment may be invalid on time-limit grounds, even where the underlying VAT figure is correct.
HMRC is asking for VAT records going years back? Our HMRC Response Support gives you a senior specialist alongside you, with a structured reply.
How information powers interact with the time limits
HMRC's powers to compel information and documents sit in Schedule 36 of the Finance Act 2008. Unlike the assessment regime, Schedule 36 has no general time limit on information requests. For documents, the legislation imposes a six-year cap unless an authorised officer agrees otherwise, but in practice that override is routine. In principle, HMRC could therefore request records of any age.
In practice, the courts have constrained that breadth. In Hegarty [2018] UKFTT 774 (TC), drawing on the older Brannigan [2006] EWHC 885 (Admin), the tribunal held that before HMRC can compel a taxpayer to produce records older than four years, HMRC must show an arguable case that the behaviour was either careless (for direct taxes) or deliberate (for VAT). HMRC cannot, in other words, go on fishing expeditions into pre-four-year history simply on suspicion.
The practical question for a business under inquiry is whether to comply with a broad Schedule 36 notice voluntarily, or to push back on scope. We see businesses concede the four-year line too readily, producing eight or ten years of records when the notice could have been challenged. Once produced, those earlier records are in HMRC's hands and can support an extended assessment if HMRC then alleges deliberate behaviour.
What this means in practice when HMRC opens a check
The standard expectation for a routine VAT compliance check is that HMRC looks at the last four years. That should be your default reference point when scoping the records to produce and the resources to commit. If HMRC asks for materially more than four years upfront, that is itself a signal: either the check has escalated, or HMRC is testing the boundaries.
If HMRC alleges deliberate behaviour at any point in the process, three things happen at once. The look-back window extends to twenty years. Penalty exposure increases materially under the inaccuracy regime (deliberate penalties run materially higher than careless, with concealed behaviour higher still). And the case begins to drift towards the civil-fraud track, with the possibility of escalation to a Code of Practice 9 investigation or, in the most serious cases, criminal referral. At that point, the question is no longer technical VAT alone; it is also about how the case is framed and managed.
The expensive misconception is that time limits will sort themselves out. They don't. The one-year evidence-of-facts rule in particular has saved many assessments from being upheld, and lost many others that should have been challenged. Documenting what HMRC knew, and when, is often the single most useful piece of work in any extended investigation.
When you might need expert VAT advisory
VAT time limits are mechanically defined but strategically nuanced. The framing of the period, the behaviour allegation, and the scope of records produced all change the outcome materially. In practice, the situations below are where a senior specialist's read makes a real difference:
- HMRC is asking for records older than four years, with no clear basis for going further back, and you want to know whether to comply or challenge the scope
- HMRC has alleged deliberate behaviour, and you want a sense-check on the strength of that characterisation before responding
- You suspect a historic failure to notify (crossing the registration threshold years ago without realising), and want to understand the exposure before making a voluntary disclosure
- You're an accountant with a long-standing client newly under investigation, and want to set the time-limit framework correctly from the outset
- You've received a late assessment covering periods more than two years old, and want to test whether the one-year evidence rule has been respected
- The case is escalating beyond a standard compliance check (talk of fraud, COP9, or criminal referral), and the time-limit framework starts interacting with much higher-stakes procedural questions
Whether you're a business owner or an accountant working on a client case, we focus on the VAT questions where extra expertise pays off, and we work in plain English.