Three academic papers published in the Institute for Fiscal Studies’ journal Fiscal Studies have delivered the most detailed critique yet of annual wealth taxation in the UK, warning that a levy like the one proposed by the Green Party of England and Wales would likely drive capital offshore, stall investment, and cost more to enforce than it collects. The lead authors, Arun Advani (University of Warwick), Helen Miller (IFS), and Andy Mayreas (IFS), released the research in early 2026 as Treasury officials face growing pressure to identify credible funding for Britain’s legally binding net-zero commitments without unsettling financial markets.
The Green Party’s 2024 general election manifesto called for a 1% annual tax on individual net assets above £10 million and 2% on assets above £1 billion, projecting it would raise billions each year for public services and climate investment. The IFS papers do not score that specific proposal, but they systematically dismantle the mechanics on which it depends. No concrete alternative revenue figure has been published by the IFS to set against the Green Party’s “billions per year” claim, in part because the papers analyse the general structure of wealth taxation rather than costing a single manifesto commitment.
The compounding cost of taxing wealth every year
The first paper, led by Advani, sets out the core economic objection. Unlike income tax, which targets a flow, an annual wealth levy hits the stock of assets repeatedly. Even at 1%, the compounding effect over a decade significantly erodes after-tax returns on capital. The authors argue that taxpayers facing such a persistent charge have strong incentives to move assets offshore, restructure holdings through trusts or corporate vehicles, or relocate entirely. A one-off levy triggers different avoidance calculations, but the annual version creates a drag on wealth accumulation that is, in the researchers’ assessment, qualitatively different from any existing UK tax.
Valuing wealth that has no market price
The second paper focuses on what the IFS calls the hardest operational barrier: putting a reliable price on assets that rarely trade. Publicly listed shares have a market value every second of the trading day. A family-owned manufacturing firm in the Midlands does not. Neither does a defined-benefit pension, a stake in a private equity fund, or a farmhouse that last changed hands in 1987.
Requiring annual valuations of these assets would impose enormous compliance costs on taxpayers and stretch HMRC’s capacity well beyond anything it currently handles. The paper treats this not as a theoretical concern but as a concrete bottleneck, grounded in how the UK’s wealthiest households actually hold their money.
Who would actually pay, and can they?
The third paper draws on the Office for National Statistics’ Wealth and Assets Survey to map the population that would be caught. Wealth at the top of the distribution is concentrated among older households and heavily weighted toward private business equity and property. These are precisely the asset classes that resist easy valuation and cannot be quickly liquidated to meet a tax bill.
Many of the people a wealth tax would target are, in the researchers’ framing, “asset rich but cash poor.” A retired couple sitting on a £12 million family business and a mortgage-free home might owe tens of thousands of pounds annually, yet have limited liquid cash to pay without selling shares or borrowing against property.
Lessons from Europe’s retreats
Several European countries have tested annual wealth taxes and pulled back. France replaced its broad impôt de solidarité sur la fortune in 2017 with a narrower levy on real-estate wealth alone, after decades of criticism that the original tax pushed wealthy residents toward Belgium and Switzerland. Sweden abolished its wealth tax in 2007 following research that documented significant capital outflows. Among OECD nations, only Norway, Spain, and Switzerland still operate broad-based wealth taxes, and each faces persistent debate about effectiveness and capital flight.
That record does not prove a UK version would fail. Britain’s tax treaties, enforcement infrastructure, and the sheer scale of its economy differ from smaller European states. But it reinforces the IFS point that behavioural responses are real and erode projected revenues quickly. The International Monetary Fund, in its October 2023 Fiscal Monitor (the most recent edition to address wealth taxation in detail), acknowledged that wealth taxes are theoretically appealing for reducing inequality but cautioned that “design details matter enormously” and that poorly constructed levies risk raising less than expected while generating significant economic distortions. Because the report is nearly three years old, its conclusions should be read alongside more recent country-level evidence.
The Green Party has not updated its costings
As of May 2026, the Green Party’s wealth-tax proposal has not advanced into legislation, and the party has not published revised costings that account for the behavioural and administrative challenges the IFS identifies. Without confirmed details on exemptions, treatment of pensions, or anti-avoidance provisions, modelling the tax’s real-world yield remains speculative.
Campaigners who support wealth taxation, including the advocacy group Tax Justice UK, have argued that the UK’s existing tax system undertaxes wealth relative to income and that a well-designed levy could reduce inequality while funding public investment. The 2020 Wealth Tax Commission, led by economists Arun Advani and Andy Summers, concluded that a one-off wealth tax was administratively feasible, though it stopped short of endorsing an annual charge. The IFS papers engage with much of that earlier work but reach more cautious conclusions about recurring levies.
Alternatives the IFS considers less damaging
The research does not argue that taxing wealth is impossible or undesirable. It argues that an annual net-worth levy is one of the least efficient ways to do it. The papers point toward alternatives that raise revenue with fewer distortions: tightening capital gains tax by closing reliefs and taxing gains at death, reforming inheritance tax to reduce avoidance through trusts and business property relief, or expanding council tax bands to capture high-value property more accurately.
A one-off wealth levy, with a clear sunset clause and robust anti-avoidance rules, also receives a more cautious hearing than an annual charge. The logic is that a single, unexpected hit gives taxpayers less time to restructure and does not create the same persistent drag on saving. But even here, the IFS warns that credibility matters: if taxpayers suspect a “one-off” levy will be repeated, they behave as though it were annual, and the avoidance problem returns.
For those who want wealth taxation to fund climate action specifically, the research suggests that earmarking revenue is a political choice, not an economic necessity. Any tax that raises revenue efficiently can, in principle, be directed toward net-zero spending. The question is whether the mechanism chosen to raise that revenue does more harm than good along the way.
A stress test most wealth-tax proposals have yet to pass
The IFS work is best understood not as a blanket rejection of taxing the wealthy but as a stress test that most current proposals fail. An annual wealth tax in the UK would need to solve the valuation problem for private businesses and pensions, build enforcement capacity that HMRC does not yet have, anticipate and counter avoidance strategies that wealthy individuals and their advisers will pursue aggressively, and accomplish all of this without triggering capital flight on a scale that wipes out the revenue gains.
None of those challenges is theoretically insurmountable. But taken together, they represent a policy design problem whose complexity the public debate has barely begun to acknowledge. Voters weighing promises of a wealth tax to fund green investment deserve to know that the gap between the slogan and a functioning system is wide, and that closing it will require far more than setting a rate and drawing a line on a balance sheet.
Warren Cohen is a finance writer based in Phoenix, Arizona, covering personal finance topics including credit, banking, and beginner investing. He earned his degree in business administration from Arizona State University and began his career working in consumer finance, where he gained direct experience with lending and credit systems. He now writes for personal finance websites and fintech platforms, focusing on clear, practical content that helps readers make informed financial decisions.
