The Amount Question and the Timing Question

The April 2026 inheritance tax reform raises two analytically separate questions: how much intergenerational business wealth should be taxed at, and when the tax should fall. This piece sets out the strongest case for each timing option (death-based, realisation-based) in its own voice, at roughly equal length, without a closing verdict from the publication.

The amount question and the timing question

The April 2026 inheritance tax reform raises two analytically separate questions: how much intergenerational business wealth should be taxed at, and when the tax should fall. Most public debate is about the first question. The second question, which a substantial share of UK tax practitioners argue is consequential for both founders and the Exchequer, has received less attention. This piece sets out the structure of both questions, presents the strongest case for each option on the timing question in its own voice, and stops there.

The piece does not adjudicate. It presupposes that the principle question — whether very large intergenerational business-wealth transfers should be taxed at all — has been engaged with separately. The principle piece sets out the strongest cases on that prior question, also without picking. A reader who concludes from that piece that the principle does not hold should treat the present piece as analytical hypothetical: if the principle were accepted, which design choice on the timing question would be better. A reader who concludes that the principle does hold should treat this piece as engaging with the consequential second question.

Where the amount question stands

The reform sets the amount at £2.5 million per individual, £5 million per couple (transferable), with 50% relief above the threshold producing an effective 20% rate, payable over ten years interest-free. HMRC's December 2025 estimate is that approximately 1,100 estates per year will be affected. CenTax (Advani, Gazmuri-Barker, Mahajan, Summers 2025) has proposed alternatives that would target the relief differently — a minimum-share rule giving £5m allowance for estates with ≥60% APR/BPR assets, or an upper limit on relief at £10m, or both combined — which they estimate could raise comparable or greater revenue while better targeting working family farms and businesses. The IFS and Resolution Foundation have welcomed the reform broadly. The Family Business Research Foundation has produced detailed analysis of the impact on family businesses specifically. The CIOT has raised practitioner-administrative concerns about valuation methodology.

The substantive disagreement on the amount question turns on (a) whether the threshold is calibrated correctly across heterogeneous cohorts (founders versus operating family businesses), (b) whether the CenTax alternative-design proposals are better-targeted, and (c) whether the spousal transferability and the £2.5m original allowance leave the regime tighter or looser than horizontal-equity considerations would support. None of these are about whether very large transfers should be taxed at all; they are about what level and what targeting does the most consistent work given that the principle is accepted. Reasonable people disagree on each question and the disagreement falls within a fairly tight range.

The timing question

The timing question is whether the tax should fall at death (the mechanism the reform adopts) or at realisation (the mechanism Australia has used for forty years for inherited assets, and which a meaningful share of UK tax practitioners argue would better serve both founders and the Exchequer). The two mechanisms produce the same broad rate against the same broad base; they differ in when the tax event occurs and what it is calculated against.

The case for taxing at death, on its strongest terms

The case for tax-at-death rests on four specific arguments, each defensible.

Administrative settledness. The UK inheritance tax framework has used death as the tax event since 1894. The valuation framework, the SAV process, the instalment regime, and the practitioner profession that supports estates through it are all built around the death-event mechanism. Switching to realisation-based timing for one asset class (unlisted trading-company shares) introduces an administrative inconsistency: estates would have one tax event for cash, listed equities, property, and other assets, and a different tax event for unlisted business shares. The Commons Library briefing CBP-10181 notes that the reform sits within the existing IHT framework precisely because that framework is administratively settled and the alternative would require building new infrastructure for a small population of estates.

Alignment with ownership transfer. Death is the moment ownership of the asset legally transfers. A tax event at the moment ownership transfers has a structural cleanness that a tax event at some indefinite later date does not: it aligns the tax point with the moment the legal relationship between the asset and its owner changes. A realisation-based regime decouples these — ownership transfers at death (untaxed), realisation happens later (taxed). The decoupling produces a class of taxpayer (the heir who has owned the asset since the testator's death and may or may not ever realise it) whose tax position is contingent on a future event the heir controls. This complicates the ordinary fiscal-administrative principle that the moment of transfer is the moment of taxation.

The lock-in problem. Auerbach (1989), Burman (1999), and the broader capital-gains realisation literature establish that lock-in effects are real: investors hold appreciated assets longer than they would in a no-tax world to defer realisation of gains. A realisation-based IHT regime for inherited unlisted business shares would produce, on this evidence, exactly the lock-in pattern the literature documents — heirs holding shares longer than they otherwise would, indefinitely deferring the tax event. The deferred tax event is, from the Exchequer's perspective, a contingent future receipt rather than a fixed near-term receipt; it can be deferred for decades through generational holding patterns, family-trust workarounds, and the kind of valuation-gaming that the Australian literature documents has emerged in their realisation-based regime. A death-based regime fixes the timing and removes the deferral incentive.

The Australian regime's actual track record. Australia's CGT-on-realisation approach for inherited assets has been criticised within Australia for producing exactly the indefinite-deferral problem above, for creating valuation-gaming incentives at the moment of inheritance (when the cost base is set), and for generating a substantial industry of family-trust structures designed to extend deferral across multiple generations. The fact that a comparator jurisdiction has used the realisation-based approach for forty years is sometimes presented as evidence the approach works; the more careful reading is that the approach has produced a particular set of administrative problems Australia has been managing, not solving. A UK regime that adopted realisation-based timing would acquire a version of these problems and a version of the practitioner industry that has grown up around managing them.

The case for taxing at realisation, on its strongest terms

The case for tax-at-realisation also rests on four specific arguments, each defensible.

The valuation problem at death. Public shares have a market price; private trading-company shares do not. When an estate holds £20 million of unlisted UK trading-company shares, HMRC and the estate must negotiate what those shares are worth at the date of death. The Shares and Assets Valuation (SAV) process exists precisely to handle this, but the process produces multi-year disputes for a meaningful share of cases, often consumes significant practitioner time on both sides, and produces values that differ substantially from any later realised value. Tax-at-realisation removes the valuation problem entirely — the tax is calculated against the actual sale price on the date of sale.

The liquidity problem at death. An estate owes tax on a number that may not match the cash available. The 10-year interest-free instalment regime softens this but does not eliminate it. Tax-at-realisation aligns the tax bill with the cash that pays it: the heir sells the asset, receives the proceeds, pays the tax out of the proceeds. The structural mismatch between an illiquid asset and a tax bill payable in cash, which the death-based regime produces, does not arise.

The pre-emptive relocation pressure. A founder who knows the tax will fall at death has a stronger reason to plan around it before death, including by relocating to a jurisdiction where the death-event tax does not apply. Tax-at-realisation creates weaker pressure to relocate pre-death because the eventual sale can occur wherever the heir lives and the founder's location at death is less consequential. The empirical magnitude of pre-death relocation in the BPR-affected cohort specifically is not well-established (the most-cited UK study, Friedman et al. 2024 LSE Working Paper, is one paper with a small interview-based sample on a different population than BPR-affected founders, and the OBR's 25% non-doms figure is from a parallel reform on a different population again), but the directional claim — that death-event taxation produces stronger pre-death migration pressure than realisation-event taxation — is uncontested in the practitioner literature.

Better-legible values, larger tax base. A realisation-based regime collects against actual sale prices, which are by construction larger and better-legible than negotiated date-of-death values. CenTax has not modelled the realisation-based alternative directly, but the practitioner case is that a realisation-based regime might raise comparable revenue from a smaller base of cases (those where actual realisation occurs) at higher per-case values, with less administrative cost.

Where each case can be tested against the other

The empirical claims on which the two cases differ are specific and, on the available evidence, not settled.

The Australian regime's documented problems with deferral and valuation-gaming are real but not catastrophic; whether the UK adopting a similar mechanism would acquire a similar set of problems, and whether those problems would be larger or smaller than the death-event valuation and liquidity problems, is an empirical question that can only be answered by running the regime. The lock-in literature establishes that realisation-based taxation produces hold-longer behaviour but does not establish the magnitude of the effect for the specific UK BPR-affected cohort. The relocation pressure under death-event taxation is documented at the practitioner level but not measured in published academic work for the BPR cohort specifically. The valuation problem under death-event taxation is documented but not quantified in revenue terms; HMRC's published statistics do not separate SAV-disputed estates from settled ones for this asset class.

A reader trying to decide which mechanism is better-suited to the UK can reach different conclusions on each empirical question and the conclusions interact. A reader who weights administrative settledness and lock-in concerns heavily, and who is sceptical of the practitioner case on relocation pressure, will prefer the death-based mechanism. A reader who weights valuation and liquidity costs heavily, and who finds the practitioner case on relocation pressure persuasive, will prefer the realisation-based mechanism. Both readings are defensible on the available evidence.

Where equivalent arguments appear in formal institutional commentary

Several of the arguments in this piece also appear in formal consultation responses, parliamentary committee reports, and professional commentary published by named institutions on the April 2026 reform. Cross-referencing them is intended to help a reader who wants to weigh the arguments at institutional level. The publication does not claim endorsement by any of these bodies; the arguments converge with material in this piece on specific questions, not as a whole.

The valuation-and-payment-timing concerns. The House of Lords Economic Affairs Finance Bill Sub-Committee report Inheritance tax measures: unused pension funds and agricultural and business property reliefs (January 2026, publications.parliament.uk/pa/ld5901/ldselect/ldeconaf/250/250.pdf) recommends extending the IHT payment deadline to 12 months for estates with qualifying APR and BPR assets, calls for a statutory safe-harbour to protect personal representatives from late-payment interest where delays are outside their control, and warns that the reforms "are likely to increase administrative complexity and exacerbate liquidity problems for estates" — all of which engages directly with the valuation and liquidity concerns presented in the case for taxing at realisation above. The Sub-Committee's recommendation that HMRC, DEFRA, and DBT "commission qualitative research to identify and understand how the reforms have affected farmers and family-business owners, and their succession planning" over seven years (Paragraph 363) is what the funding-stack piece's central-case observation about the absence of cohort-specific behavioural data points at.

The administrative-burden concerns. The Chartered Institute of Taxation has submitted formal consultation responses on the draft legislation (tax.org.uk/ref1551) and on the trusts aspect of the reform (tax.org.uk/ref1481). The CIOT and ATT joint commentary in Tax Adviser (post-Budget 2025, taxadvisermagazine.com) records that some CIOT and ATT recommendations on the design were partially adopted (transferable spousal allowance) and others were not (allocation of the allowance to specific assets; gifting transitional rules). The CIOT-ICAEW concern about valuation administrative burden is referenced in the Commons Library briefing CBP-10181.

The horizontal-equity argument supporting the principle. The Institute for Fiscal Studies (Adam, Miller, Sturrock 2024, Inheritance tax and farms) and the Resolution Foundation Budget 2024 briefing (cited via the House of Lords Library) make the horizontal-equity case set out within the case-for-taxing-at-death section above. Both bodies have published their positions on the BPR/APR reform broadly accepting the principle of bringing concentrated business wealth into the tax base.

The CenTax alternative-design proposals. The Centre for the Analysis of Taxation (Advani, Gazmuri-Barker, Mahajan, Summers 2025, centax.org.uk) proposes a minimum-share rule and an upper limit on relief as alternatives to the threshold-only design — design alternatives that the long article's Position D does not engage with at depth, but which sit in the same family of scope-adjustment proposals. CenTax's analysis is grounded in HMRC inheritance tax data 2018-2022 and is a stronger empirical foundation for design alternatives than the publication's own work.

The cohort-impact research. The Family Business Research Foundation report Business Property Relief and Family Firms in the UK: From Relief to Reform (Kemp 2025) and the FBRF/Cebr research project on the impact of BPR reforms on UK family businesses (interviews running December 2025 to May 2026) are the most direct UK-cohort-specific work on the operational concerns the funding-stack piece engages with. fbrf.org.uk.

The set of institutional sources above is not exhaustive. Other formal consultation responses (ICAEW, the Country Land and Business Association, the National Farmers' Union, the Confederation of British Industry, individual major firms including Saffery, KPMG, BDO, Deloitte, Royal London, BKL, PKF Francis Clark, and Hatchers) have engaged with specific aspects of the reform. The sources page maintains the fuller reference stack.

How this piece relates to the operational pieces

The publication's operational analysis (the long article, the funding-stack technical companion, the policy options paper) presents the design positions on the timing-and-mechanism question — A, B, C, D — at equal length. Position A holds the existing death-event mechanism with practical fixes; Position B switches to CGT-on-realisation; Position C defers the mechanism question pending evidence (with or without triggers variants); Position D raises the threshold for qualifying unlisted trading-company shares within the existing mechanism. The publication does not pick among them. This piece engages with the underlying timing question that A and B disagree on; it does not adjudicate either.

A reader who has read this piece carefully has the structural inputs to weigh A and B against each other, and to read C and D as variants on the timing-question framing. The interactive financial model in the operational suite makes the dependencies between the timing-question parameters and the fiscal outcomes legible; a reader can adjust the assumptions about pre-death relocation, valuation-dispute frequency, and lock-in deferral to see how the fiscal balance changes under each mechanism. The model does not output a recommended mechanism; it outputs the consequences of a parameter set, given the user's choice of inputs.

Written by Claude (Anthropic). Not edited into Doug's voice. An earlier version of this piece took a position — that the timing question matters more than the amount question, and that realisation-based timing is preferable to death-based — and presented that position as the publication's view. A reviewer (1 May 2026) noted that the publication had been claiming neutrality on the homepage while taking positions in this piece and in the principle piece, and recommended either declaring the position openly throughout the publication or rewriting the position-taking pieces to genuinely not adjudicate. Doug chose the second path. The piece has been rewritten to set out the strongest case for each timing mechanism (death-based and realisation-based) at roughly equal length, in the voice of its strongest defender, without a closing verdict from the publication. The empirical literature cited remains: Auerbach (1989) and Burman (1999) on capital-gains lock-in; Friedman, Gronwald, Summers and Taylor (2024), Tax flight? Britain's wealthiest and their attachment to place, LSE III Working Paper 131; the Australian regime's documented track record on deferral and valuation-gaming. Earlier rounds of corrections logged on the corrections page document the literature drawn on for the original position-taking version. Corrected on 1 May 2026: the piece has been substantially rewritten to remove its closing verdict and present the timing question as genuinely contested between two defensible mechanisms, in line with the publication's stated posture of not adjudicating.