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    TaxKilnUK tax guidance

    Tribunals + HMRC Enquiries → Enquiry types + time limits

    HMRC Enquiry Types + Time Limits — s.9A Formal, s.29 Discovery, FA 2008 Sch 36 Information Notices

    HMRC has three procedural routes into a taxpayer's affairs. (1) A formal Self Assessment enquiry under TMA 1970 s.9A must be opened within 12 months of the filing date (or amendment) — once that window closes, HMRC needs (2) a discovery assessment under TMA 1970 s.29, which requires a 'discovery' of an under-assessment AND staleness/behaviour conditions to extend the time limit. (3) Information notices under FA 2008 Sch 36 can be issued in either context, with statutory protections for legally privileged material + a tribunal-approval route for third-party notices. The time limit depends on taxpayer behaviour: 4 years (normal recovery), 6 years (carelessness), 12 years (offshore — FA 2019 s.80 + Sch 11 inserting TMA 1970 s.36A), or 20 years (deliberate). Understanding which route HMRC has used + which time limit applies is the foundation of every enquiry response.

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    In plain English

    HMRC cannot open a 'formal enquiry' into a Self Assessment return forever — only within 12 months of the filing date (TMA 1970 s.9A). After that window closes, HMRC can still come back, but only via a 'discovery assessment' under s.29, which has stricter conditions. Either way, HMRC's information-gathering powers come from FA 2008 Schedule 36, which is the same statutory regime regardless of which enquiry route is used. The time-limit ladder is the most important thing to understand. If HMRC believes you made an innocent error, they have 4 years to recover the under-assessed tax. If they believe you were careless (failed to take reasonable care), it extends to 6 years. If they believe the under-assessment relates to offshore income/gains, it extends to 12 years (FA 2019 reform — corrected from earlier FA 2015 framing; the actual statute is FA 2019 s.80 + Sch 11 inserting TMA 1970 s.36A, in force from 6 April 2019). If they believe the under-assessment was deliberate, it extends to 20 years. The behaviour category is therefore the central battleground in most enquiries. HMRC has an incentive to push for 'careless' (extends time + opens penalty regime). The taxpayer has every incentive to evidence reasonable care taken at the time. Statute, manual, and case law (Perrin v HMRC, Hicks v HMRC, Tooth v HMRC) all converge on a fact-specific reasonableness assessment. For most readers, the first move on receiving an enquiry letter is: identify the statutory route (s.9A vs s.29 vs Sch 36), check the time limit applicable to the year(s) under enquiry, and assemble the contemporaneous documentation supporting the position taken on the return. Most enquiries close at this stage without penalty if records are organised.

    How it works

    Route 1 — Formal SA enquiry (TMA 1970 s.9A)

    HMRC issues a notice under s.9A within 12 months of the filing date (31 January for an on-time online return). The notice does not need to state the reason. Once opened, HMRC has wide latitude to ask questions + issue Sch 36 information notices. The enquiry ends only by a closure notice (s.28A) — either issued by HMRC or directed by the FTT on taxpayer application. There is no statutory deadline on HMRC to close an enquiry, but the FTT will typically direct closure where HMRC cannot articulate what outstanding question remains.

    Route 2 — Discovery assessment (TMA 1970 s.29)

    Used where the s.9A window has closed. HMRC must show: (a) an under-assessment of tax has been 'discovered'; AND (b) either (i) the taxpayer or agent was careless/deliberate, OR (ii) the hypothetical HMRC officer with the s.9A enquiry window open could not reasonably have been expected to be aware of the under-assessment from the information provided. The Supreme Court in Tooth [2021] confirmed 'discovery' has a low threshold (newly arrived at conclusion suffices) but the conditions in (b) are the real protection. The hypothetical-officer test from HMRC v Charlton [2012] is the operative authority on (b)(ii).

    Route 3 — FA 2008 Sch 36 information notices

    Three types: (a) taxpayer notice (para 1) — direct to the taxpayer for documents/information reasonably required to check tax position; (b) third-party notice (para 2) — to someone else (bank, employer, customer) for the taxpayer's information; (c) identity-unknown notice (para 5) — to discover taxpayer identity. Third-party notices require tribunal approval (para 3) unless the taxpayer agrees. Legal professional privilege (para 23 / para 18) protects communications with solicitors; the narrower 'tax adviser privilege' (para 24A introduced by FA 2012) protects only specific advice documents from accountants/tax advisers — NOT general working papers. Appeal against a Sch 36 notice is to the FTT under para 29; review (not appeal) for third-party notices.

    Time limits — the behaviour ladder

    Default: 4 years from end of relevant tax year (TMA 1970 s.34). Careless behaviour: 6 years (TMA 1970 s.36(1)). Deliberate behaviour (or deliberate concealed): 20 years (TMA 1970 s.36(1A)). Offshore matters (income/gains from a territory outside the UK): 12 years (TMA 1970 s.36A inserted by FA 2019 s.80 + Sch 11, in force 6 April 2019 for ITax/CGT and 1 April 2019 for IHT). 'Offshore matter' includes income arising in / assets situated in / activities carried on in a territory outside the UK. The 12-year limit is the corrected position — earlier informal references to FA 2015 s.117 (which dealt with strict-liability offshore offence) are wrong for time-limit purposes.

    Behaviour categories — the central battleground

    Four categories (under Schedule 24 FA 2007 penalty framework, also relevant for time limits): innocent error (no penalty, 4-year limit), careless (failure to take reasonable care — 6-year limit + 0%-30% penalty), deliberate but not concealed (knew the return was wrong — 20-year limit + 20%-70% penalty), deliberate and concealed (knew + actively concealed — 20-year limit + 30%-100% penalty). HMRC has an incentive to push 'careless' because it extends the time limit + opens penalty. The taxpayer should evidence: contemporaneous record-keeping; reliance on competent accountant; following published HMRC guidance at the time. Christine Perrin v HMRC [2018] UKUT 156 (TCC) provides the structured 4-stage analysis adopted across the FTT.

    Who this applies to + key conditions

    Statute + manual references

    Primary: TMA 1970 s.9A (formal SA enquiry — 12 months from filing); TMA 1970 s.29 (discovery assessment); TMA 1970 s.34 (normal 4-year time limit); TMA 1970 s.36 (6-year careless / 20-year deliberate); TMA 1970 s.36A inserted by FA 2019 s.80 + Sch 11 (12-year offshore); FA 2008 Sch 36 (information + inspection powers).

    Related: TMA 1970 s.28A (closure notice ending a s.9A enquiry); TMA 1970 s.31 (appeal against discovery assessment); TMA 1970 s.106A (criminal evasion offence; inserted by FA 2000 s.144 — corrected from FA 2001 s.114); FA 2008 Sch 36 para 18 (legal professional privilege); FA 2008 Sch 36 para 21 (tax adviser privilege — narrower than LPP); FA 2008 Sch 36 para 23 (third-party notice tribunal approval); Schedule 18 FA 1998 (CT return enquiry framework — equivalent of TMA 1970 for companies)

    HMRC manual: EM1500 (opening an enquiry); EM3200 (discovery); CH200000 (information powers); CH50000 (offshore time limits)

    Case law: Tooth v HMRC [2021] UKSC 17 (discovery + staleness); Hicks v HMRC [2020] UKUT 12 (TCC) (discovery + officer awareness); Jonas v HMRC [2017] UKFTT 392 (deliberate behaviour); Auxilium Project Management v HMRC [2016] UKFTT 249 (careless vs deliberate); HMRC v Charlton [2012] UKUT 770 (TCC) (hypothetical officer test for discovery)

    Common mistakes + traps

    Worked example

    Priya, a sole-trader graphic designer, files her 2024/25 SA return on 31 January 2026 showing self-employment profit of £52,000

    On 15 November 2026 (within the 12-month s.9A window which closes 31 January 2027), HMRC opens a formal enquiry under s.9A, asking for bank statements + invoicing records + a sample of client contracts. Priya is concerned because she included £8,000 of cash payments in her records but is not sure her categorisation of certain personal vs business expenditure was 100% correct.

    1. Step 1 — Identify route: TMA 1970 s.9A formal enquiry, opened within 12 months — standard.
    2. Step 2 — Respond within 30 days acknowledging receipt + indicating cooperation. Request copy of HMRC's specific lines of concern (not always given but worth asking).
    3. Step 3 — Time limit for under-assessment: 4 years from end of 2024/25 (i.e. to 5 April 2029) under TMA 1970 s.34, extendable to 6 years if careless, 20 years if deliberate.
    4. Step 4 — Provide requested documents in scope + ONLY in scope. Sch 36 reasonableness test (para 1) is the protection against over-broad requests.
    5. Step 5 — If HMRC identifies expense categorisation errors and asserts 'careless' behaviour: contest by evidencing the contemporaneous decision-making process — reliance on accountant + HMRC guidance + nature of items (genuine ambiguity vs negligent omission). Perrin v HMRC [2018] UKUT 156 (TCC) provides the structured reasonableness analysis.
    6. Step 6 — Suppose HMRC proposes a £3,200 under-assessment (additional tax on £8,000 disallowed expenses at higher rate). If accepted as innocent error: no penalty, just the additional tax + late-payment interest (4% over BoE base from 6 April 2025 per HMRC late-payment rate). If HMRC pushes 'careless': £3,200 + up to 30% penalty (£960) + the 6-year time limit cracks open earlier years.
    7. Step 7 — If unable to agree, request a Closure Notice under TMA 1970 s.28A(4) — FTT can direct closure if HMRC cannot articulate outstanding lines. The discovery + appeal path then opens via Form T240 (see /tribunals-and-hmrc-enquiries/statutory-review-and-ftt-procedure).

    Outcome: Most s.9A enquiries close on this kind of fact pattern with: agreed adjustment, no penalty (innocent error) OR 0%-15% penalty (careless with full disclosure during enquiry), and late-payment interest. The case is well within self-serve + qualified accountant scope. Penalty-specialist firm engagement at £3,000-8,000 is materially disproportionate to the underlying figures + outcomes available without it.

    How this connects to the rest of the framework

    Penalty regime + reasonable excuse →

    Behaviour categories (careless / deliberate / deliberate concealed) drive both time limit (this page) AND penalty percentage (penalty-regime page) — same statutory framework.

    Statutory review + FTT procedure →

    Discovery assessment + closure notice + Sch 36 notice are all appealable to FTT via statutory review then Form T240.

    COP9 + CDF →

    If HMRC suspect serious civil tax fraud, the COP9 route may be used INSTEAD of s.9A — different procedural framework with 60-day Outline Disclosure window.

    Voluntary disclosure mechanisms →

    If taxpayer prompts disclosure BEFORE HMRC enquiry, penalty regime is materially reduced (unprompted vs prompted) + behaviour assessment more favourable.

    /self-assessment →

    Self Assessment filing + amendment timing determines the s.9A enquiry window opening.

    /moving-abroad/uk-source-income-non-resident →

    Offshore matters definition under TMA 1970 s.36A interacts with non-resident UK-source income reporting obligations.

    Frequently asked questions

    What happens if I miss the Self Assessment deadline?+
    The Self Assessment deadline is 31 January (online filing) for the previous tax year. Miss it and HMRC apply an automatic £100 penalty. Beyond that: £10 per day from 3 months late (capped at £900), 5% of tax due at 6 months late, and another 5% at 12 months late, under Schedule 55 of the Taxes Management Act 1970. If you have a genuine reason (serious illness, bereavement, technical issue with HMRC's systems) you can appeal with evidence; HMRC accepts reasonable excuse appeals in most genuine cases.
    Do I need an accountant or can I file Self Assessment myself?+
    Legally you can file Self Assessment yourself via gov.uk for free, most simple sole-trader returns (single income source, basic expenses) are realistic to self-file. An accountant adds real value when: your trading profit is above £40,000 (extraction-strategy decisions matter), you have multiple income streams (PAYE + self-employment + property + dividends), you've crossed the £90,000 VAT threshold, you're considering incorporation, or you have an HMRC enquiry. Expect to pay £400-£1,500/year for a typical sole-trader accountant; the cost is itself a deductible expense.
    How do payments on account work?+
    When your Self Assessment tax bill exceeds £1,000 for the first time, HMRC requires payments on account toward NEXT year's tax. Half the current bill is due 31 January (alongside the current bill); the other half is due 31 July. So your first January after crossing the threshold can hit with a double-bill: last year's balance + first payment on account. Adjust via Form SA303 if you expect next year's income to drop substantially. Payments on account don't apply if more than 80% of your tax is collected via PAYE.
    How do I know if HMRC has opened a formal s.9A enquiry vs an informal review?+
    A s.9A enquiry MUST be opened by formal notice citing s.9A (or s.12AC for partnerships; Sch 18 para 24 FA 1998 for companies). Informal letters asking general questions do NOT count + you are not obliged to respond beyond reasonable courtesy. If in doubt, write back asking HMRC to confirm whether they are opening a formal enquiry under s.9A.
    Can HMRC issue a Sch 36 notice without an open s.9A enquiry?+
    Yes — FA 2008 Sch 36 is independent of the s.9A enquiry framework. HMRC can issue a taxpayer notice 'for the purpose of checking the taxpayer's tax position' at any time, subject to reasonableness + time-limit constraints. This is the pre-enquiry information-gathering power.
    What's the difference between 'careless' and 'deliberate' for time-limit purposes?+
    Careless: failed to take 'reasonable care that a prudent and reasonable taxpayer would take' (Sch 24 FA 2007 para 3). Deliberate: knew the return was wrong + sent it anyway. The line between them is the central battleground. Auxilium Project Management v HMRC [2016] UKFTT 249 + Jonas v HMRC [2017] UKFTT 392 give FTT analysis frameworks.
    Is the 12-year offshore time limit really 12 years not 4?+
    Yes for offshore matters — TMA 1970 s.36A inserted by FA 2019 s.80 + Sch 11 sets the limit at 12 years regardless of behaviour (i.e. it is more than the 4-year normal limit but less than the 20-year deliberate limit). For tax years from 2013/14 onwards.

    Free + regulated-body resources

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