High-net-worth estate planning: the liquidity event, concentrated wealth, and the next principal

• The US federal estate, gift and generation-skipping exemption is US$15 million per person from 1 January 2026, indexed for inflation, with 40% above it, made permanent by the One Big Beautiful Bill Act of July 2025.

• UK business and agricultural property relief is capped from 6 April 2026: 100% relief on the first £1 million of qualifying assets, 50% above it, an effective 20% rate; AIM shares get 50% only.

• Planning done before a sale, while shares are private and their value uncertain, can move a large part of the gain to the next generation at a fraction of the tax; the same planning after completion cannot.

Below the exemption, an estate plan is about the right people getting the right things with no fuss. Above it, three things change. Tax becomes a design constraint rather than a footnote, so structure starts to matter more than the will. The assets stop being simple: a private company, a concentrated stock position, property in two countries, art. And the number of people who depend on the principal's judgement, family and staff and advisers, grows faster than the money. The plan has to cover all three.

A liquidity event is the moment illiquid ownership becomes cash or listed shares: a sale, a listing, a recapitalisation. Everything valuable in estate and tax planning around it happens before completion, while the value is still arguable and the shares are still private. After completion the value is a number on a bank statement and the options close.

The family side of the same twelve months is less discussed and decides more. The sale is when heirs learn what the family is worth, when spouses learn what the plan says, and when the founder has to answer the question that has been deferred for a decade: what is the money for. Families that use the year before the sale to hold the meeting, write the constitution and say the reasons out loud arrive at completion as a family. Families that do not, arrive as a cap table.

A founder's estate is often one thing: the company, or the stock that came from it. A single position carries a single risk, and the estate plan has to say what happens to it, who can sell it, and on what terms, when the founder is not there to decide. The instruments are known: diversification programmes and 10b5-1 plans for listed stock, exchange funds and collars in the United States, trusts that hold the shares with a protector who understands the business, buy-sell agreements with co-owners (the funding question), and a written policy on when the family sells. The judgement about the company, its people, its customers and its price, is not an instrument. It was the founder's, and it goes with the founder unless it was recorded.

A probated will is a public document. A family with a public estate has a public target. Above the threshold, privacy is a planning goal in itself: revocable trusts in the United States, trusts and nominee arrangements elsewhere, holding companies for property, and a deliberate choice about which country's register the family appears in (the United Kingdom's register of overseas entities, the EU's beneficial-ownership registers, the US Corporate Transparency Act reporting that now exempts domestic companies). Security follows: the family that appears on a rich list plans for it, and the plan includes who in the family is told what, and when.

A family office is the institution a family builds when its affairs outgrow its advisers: investments, tax, legal, reporting, philanthropy and governance under one roof. The single-family office usually makes sense above about one hundred million dollars, where the cost of the staff (one to two percent of assets a year at the smaller end) is smaller than the cost of not coordinating them; the multi-family office starts far lower, at ten to twenty million. The question that decides it is less the number than the number of decisions a week that currently land on one person. The family office as the memory of the family is the full treatment, including the office's own succession.

Above the threshold, where the principal lives is a planning variable. The United Kingdom's 2025 switch from domicile to residence brought a wave of departures to Italy, Switzerland, Dubai and Singapore; the United States taxes its citizens wherever they live, so an American principal's move changes state tax and nothing federal; Australia's departure triggers a deemed disposal of most assets other than real property. Every move has a tax cost on the way out, a residence condition on the way in, and a succession law waiting at the end, and the family that moves for the tax usually discovers the succession law at the notary. Where to base a family office compares the four places families actually choose between.

Every family at this scale has a next principal, whether or not it has chosen one. Money-ready and decision-ready are different things. An heir who has been told what the family owns is money-ready. An heir who has decided things, with real stakes, and been allowed to be wrong, is decision-ready. The families that survive the transfer give the next principal decisions early: a foundation to run, a property to manage, a seat at the meeting with a vote. The ones that do not hand over a balance sheet to someone who has only ever received.

The heir who will not run it needs a different plan: a fair share, a structure that keeps the asset with the sibling who will, and a relationship between them that the plan did not poison. That is the equalisation problem, and it is usually solved with a trust, a buy-out and life cover (life insurance inside the estate plan).

Nothing here replaces the private-client lawyer, the accountant or the wealth manager; above the threshold, all three are in the room and should be. What the profession cannot supply is the principal's own account of how they decide, for the day the principal is not there and the office, the heirs and the advisers are all asking what she would have done. That account can be built now, in the principal's own words, and held for exactly that day.