Most property landlords incorporate, accept the default accounting reference date (ARD) Companies House assigns at incorporation, and never revisit it. That is a missed planning lever. The ARD is the one company-law parameter you can re-set at will under Companies Act 2006 section 392, and the timing of the corporation tax cycle has direct consequences for personal Self Assessment alignment, section 455 cashflow on a director's loan, capital allowance recognition before a disposal, and the wider household-level tax position where the founder also holds property personally.

This page works through the CA 2006 s.392 mechanic (shortening is unlimited, lengthening is restricted once every five years and to a maximum 18 months), the Companies House AA01 filing route, and three applied use cases for a property SPV. It is the strategic lever, not the tactical "things to do before year-end" checklist (for which see our end-of-tax-year landlord checklist covering the actions inside an existing period). The choice of when the year-end falls in the first place is what we cover here.

The CA 2006 s.392 mechanic, in one paragraph

Companies Act 2006 section 392 sets the rules for altering the accounting reference date. Two asymmetric routes:

  • Shortening the current accounting period (bringing the year-end earlier). Unlimited. Companies House form AA01, filed at any time before the current period ends. There is no statutory waiting interval; you can shorten in successive years if you want to.
  • Lengthening the current accounting period (pushing the year-end later). Restricted: once every five years from the end of any previously lengthened period, and the resulting accounting period cannot exceed 18 months. The five-year clock resets only after each lengthening.

Limited exceptions to the lengthening restriction apply where the company is in administration, where the change brings the ARD into line with a parent company's ARD, or where Companies House grants special dispensation; in practice those exceptions are rare for a single-director property SPV.

The corporation tax consequences follow company law. Where the period is shortened, a short stand-alone accounting period is created (typically a few months); the corporation tax return is filed on the new short period basis with normal nine-month-and-one-day payment timing from the new ARD. Where the period is lengthened, the new longer period (up to 18 months) is a single corporation tax accounting period; payment is nine months and one day after the new ARD. The administrative detail is in HMRC's Company Taxation Manual at CTM93000 onwards.

Use case one: aligning the SPV year-end with personal Self Assessment

The personal Self Assessment year runs 6 April to 5 April. Where the property landlord also holds property personally outside the SPV and files an SA100 with a UK Property pages (SA105), the SPV's ARD effectively determines whether the family-level tax planning fits into a single review cycle or two staggered ones.

Why 31 March (or 5 April) is the common alignment

A 31 March ARD gives the company a 12-month accounting period running 1 April to 31 March. The corporation tax return (CT600) is due 12 months after the ARD (so by 31 March the following year); the payment is due nine months and one day after the ARD (so 1 January of the same year). The personal SA filing is due 31 January for the tax year ending the previous 5 April. The two cycles produce a clean dual deadline: by 31 January, both the personal SA and the corporation tax payment for the prior ARD are settled.

For a landlord running MTD ITSA on a personal portfolio (qualifying income above £20,000 from April 2027, with the original April 2026 cohort already in scope for those above £50,000), the alignment matters more. The MTD ITSA quarterly cycle runs 6 April to 5 July, 6 July to 5 October, 6 October to 5 January, 6 January to 5 April, with an End of Period Statement and Final Declaration submitted afterwards. A 31 March or 5 April SPV ARD lets you reconcile the SPV's full-year position against the MTD ITSA cycle in a single annual review.

Where 31 December is the right choice instead

A 31 December ARD gives you a longer window between the corporation tax year-end and the personal SA deadline. Dividends declared in the first quarter of the following calendar year can be timed to land in either the current or next personal tax year, depending on whether the declaration date is before or after 5 April. For founders whose personal income fluctuates year to year (consultancy work, employment plus dividend), the 31 December ARD gives extra dividend-timing flexibility.

The trade-off is cycle separation. The SPV's audit / accounts work runs January to September of the following year; the personal SA cycle runs the same year for the previous tax year. The two cycles do not overlap, which means two separate annual review cycles rather than one.

Use case two: deferring a profit-spike year-end or section 455 timing

Section 455 director's loan timing

An overdrawn director's loan account at the end of an accounting period attracts a corporation tax charge under CTA 2010 section 455 at the dividend upper rate set by ITA 2007 s.8(2) for the tax year in which the loan is made: 33.75% for loans made before 6 April 2026 and 35.75% for loans made on or after 6 April 2026 (per FA 2026 s.4(1)(b) substituting s.8(2)). The charge is payable nine months and one day after the period end and recoverable on later repayment of the loan. The charge is permanent if the loan is never repaid; the cashflow exposure is the gap between paying the s.455 charge and reclaiming it after repayment.

Where a director is sitting on a temporarily overdrawn DLA at the planned year-end (a refinance has injected cash personally that will be re-lent back to the company shortly, or a personal expense has been paid by the company and will be reimbursed), an ARD change can move the year-end past the expected repayment date and eliminate the section 455 trigger entirely. The mechanic:

  1. Confirm the expected repayment date for the DLA debit balance.
  2. File AA01 to shorten the current accounting period to end after the repayment date (or, if the period is short and lengthening is available under the once-every-five-years rule, lengthen the period to bridge across the repayment date).
  3. The DLA is in credit at the new ARD; s.455 does not engage.
  4. Corporation tax return filed on the new period with the credit DLA position.

This is mainstream tax planning, not avoidance. The s.455 charge is the law on overdrawn balances at the period end; an ARD change moves the period end. The historic targeted anti-avoidance rules in CTA 2010 ss.464C and 464D (in force pre-30 October 2024, since omitted in full by FA 2025 s.81(3)(b)-(4)) caught deliberate round-trip clearance patterns (clear the DLA before period end, re-borrow shortly after); for post-30-October-2024 periods, the residual s.464A arrangement-benefit charge plus HMRC's wider arrangement-or-intention reading catch the same patterns. Neither historic nor current architecture catches a legitimate ARD adjustment. See our companion DLA mechanics page for the full s.455 timeline and our DLA bed-and-breakfast trap deep-dive for the post-FA-2025 architecture.

Profit-spike deferral across reform dates

Where a known statutory change is coming (a new corporation tax rate, a new rule that affects the SPV's tax position, a new IHT cap that engages on or after a date in the future), an ARD change can move the year-end across or before the reform date depending on whether the change helps or harms.

The April 2026 BPR / APR £1m cap is one such reform, but as discussed in our wider IHT material, the cap only matters where the property qualifies for BPR in the first place, which pure BTL does not (the Pawson investment-line test). For most pure-BTL SPVs the £1m cap is not engaged. Where the SPV holds a serviced-accommodation business that might qualify for partial BPR, the ARD has a marginal effect on the value reported at the IHT transfer date.

A more common profit-spike scenario is a one-off transaction (large insurance receipt, capital allowance balancing charge on disposal of a furnished holiday let pre-FHL-abolition transition, dilapidations settlement). Where the receipt is timing-flexible, shortening or lengthening the ARD to push the recognition into a later or earlier period can shift the marginal corporation tax rate the receipt is taxed at (between the 19% small profits rate, the 26.5% marginal-relief band, and the 25% main rate).

Use case three: bringing a year-end forward before a known disposal

Where the SPV has a property disposal planned and the current period has a capital allowance pool, a trading loss, or other tax assets that would set off against the gain, the question is which accounting period the disposal should fall into.

The capital allowance pool consideration

A property SPV has a capital allowance pool covering plant and machinery in any commercial units, fixtures eligible for super-deduction or full expensing, and (for an SPV with mixed-use property) any structures and buildings allowance pool. The pool generates writing-down allowances annually; on disposal of the relevant asset, a balancing event reconciles the pool against the disposal proceeds.

Where a disposal is planned and the SPV's current period has a healthy capital allowance position, the strategic question is whether to crystallise the disposal in the current period (use the current pool against the gain) or push it to the next period (preserve the pool for future periods). The answer depends on the size of the gain relative to the pool and the SPV's expected income in the next period. An ARD change can effect the timing without forcing the underlying transaction to move.

Worked scenario: an anonymised disposal

A property SPV with a single commercial unit (a small retail premises let to an unconnected tenant) has a £40,000 capital allowance pool covering shop fittings and a £25,000 SBA pool on the structure. The premises are under offer for £450,000 against a base cost of £300,000, generating a gain of £150,000. The current accounting period runs to 31 March 2027 and the disposal is expected to complete in May 2027.

Option A (no ARD change): the disposal completes in the next accounting period (1 April 2027 to 31 March 2028). The capital allowance pool is available in the next period and sets off against the disposal gain to the extent of the pool. Corporation tax on the gain (assuming a small-profits-rate company on a single property): roughly (£150,000 - £40,000 - £25,000) × 19% = £15,960.

Option B (ARD lengthened to 31 May 2027 to bring the disposal into the current period): the disposal completes in the lengthened period. The capital allowance pool is the same. The corporation tax calculation produces a substantially similar result. The difference is timing: Option A defers the tax payment to 1 January 2029 (nine months and one day after 31 March 2028); Option B brings it forward to 1 March 2028. The cashflow planning is the only material difference.

Option C (ARD lengthened past 31 March 2027 to absorb both the pre-disposal trading and the post-disposal balancing): a single 14-month accounting period 1 April 2026 to 31 May 2027. The capital allowance pool is recomputed for the longer period (14/12 of the standard annual writing-down allowance), giving roughly £46,667 of pool. Slightly more relief; tax bill marginally lower at approximately (£150,000 - £46,667 - £25,000) × 19% = £14,893.

The right option depends on the SPV's wider position. The point is that the ARD is the planning lever; the underlying transaction does not need to move.

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The Companies House AA01 filing in practice

The AA01 form is filed online at the Companies House WebFiling service (or by post on the paper version, but online is the standard route). The form requires:

  • The company number.
  • The current ARD (auto-populated from Companies House records).
  • The new ARD.
  • The current period to which the change applies (shortening only) or the period to which the change applies (lengthening).
  • A declaration that the company is entitled to make the change under CA 2006 s.392 (specifically that the once-every-five-years rule has not been broken in a lengthening case).

The change takes effect immediately on filing. Companies House updates the company record within a few working days. There is no Companies House fee for the change. HMRC is notified automatically through the Companies House update; you do not need a separate HMRC filing.

Where the change involves a short stand-alone period (a shortening case), the company files a corporation tax return for that short period on the standard timetable. HMRC's CTM01405 guidance covers the straddling rule for short periods. Where the change creates a longer-than-12-month period (a lengthening case), the period is a single corporation tax accounting period up to 18 months; a period exceeding 18 months would split for corporation tax purposes under Finance Act 1998 Schedule 18 paragraph 3, but s.392 prohibits a period over 18 months in any case.

What to do before filing an AA01

Five checks our team works through with founders before any AA01 filing:

  1. Verify the once-every-five-years rule is not breached (lengthening only). Check Companies House records for any previous AA01 lengthening within the last five years.
  2. Confirm the new ARD aligns with the planning objective. Run the corporation tax payment date and the corporation tax return filing date for the new ARD; check both fit the planned cashflow and accountant capacity.
  3. Check the impact on the corporation tax computation. Where the change creates a short or long period, the capital allowance pool, the marginal-relief band ranges, and the small-profits-rate threshold all adjust pro rata. Run a quick projection of corporation tax under the new period before filing.
  4. Confirm no outstanding statutory filings on the existing ARD. Accounts overdue on the existing ARD must be filed before the new ARD takes effect; the AA01 does not cure the late filing.
  5. Notify any external stakeholders that depend on the year-end. Lenders running covenant tests on a date-specific basis, auditors (if any), and any contractual counterparties referring to "the company's financial year". Most BTL SPVs have no such stakeholders; if any exist, a courtesy notification before filing avoids confusion.