Incorporating a property portfolio: the British saving that creates an American problem

Figures relate to tax year 2025-26 (UK) · 2025 (US)

Your accountant suggests moving the rental flats into a limited company. The rules on loan interest have pushed your British tax bill up. A company would fix that. Incorporation relief can defer the capital gains tax on the transfer, which makes the idea look straightforward.

For an American landlord it is not. The company that solves the British problem becomes a foreign firm in American eyes. It brings its own forms and its own tax. So this guide covers what the relief does, what incorporation costs, and what the American return makes of it.

Key takeaways

• Incorporation relief can defer capital gains tax when a property business transfers to a company.
• The relief needs a real business moved as a going concern, not a passive portfolio.
• Stamp duty usually applies on market value. It is the biggest cost on day one.
• An American owner gains a foreign company, with yearly forms and possible tax on profits left inside it.
• Tax the company pays here does not credit against your own US tax.
• An entity election changes how America sees the company, and it has its own cost.

What is incorporation relief?

It is the British relief that defers capital gains tax on a transfer. You move a business into a company and take shares in return. For a landlord sitting on years of growth, that deferral is the whole attraction.

According to HMRC guidance, the relief applies automatically where the conditions are met. All the assets of the business, apart from cash, must transfer, and the consideration must be shares in the company.

Does a property portfolio qualify?

Only where it counts as a business, not a passive investment. HMRC looks at how active you are: the number of properties, the hours worked, and who does the managing. A few flats run by an agent rarely qualifies. A large self-managed portfolio may.

This is the first place the plan fails. Landlords hear about the relief, assume it applies, and discover the activity test only when the transfer is already done.

Test it first. Ask how the work is done. Then count the hours.

The costs nobody mentions first

Stamp duty land tax usually applies on the market value of the properties. You and the company count as connected persons. Additional and higher rates can apply on top. For a portfolio worth £2 million that charge alone can run into six figures.

Partnership relief can reduce or remove the charge where the business genuinely runs as a partnership first. That route has its own conditions, and HMRC examines it closely.

Mortgages add friction too. Lenders must consent to the transfer, and company borrowing usually carries a higher rate than personal buy-to-let lending.

Ask the lender early. Get it in writing. Budget for a higher rate.

What changes on day one?

Ownership. The properties belong to a company, and you own shares. Rent now lands in the company, not in your bank account. Every pound you take out becomes a separate decision, with its own tax.

That shift is bigger than it sounds. Many landlords miss the cash flow effect. Money that once arrived each month now sits behind a corporate wall.

Rent goes in. Tax comes out. What is left is the company's money, not yours.

Does the mortgage interest saving still work?

Yes, inside the company. A company deducts finance costs in full against rental profit, while an individual landlord gets only a basic rate credit. That gap drives most incorporations, and for a heavily mortgaged portfolio it can be worth thousands each year.

Weigh it against the cost. Stamp duty, legal fees and higher lending rates come first. The saving then has to outrun them for years.

The saving is real. It is also slow. Incorporation relief covers the gain, but it does nothing for the stamp duty that arrives first.

What happens on the American side?

Per the IRS rules on foreign corporations, the company becomes a controlled foreign corporation, or CFC, once Americans own more than half. That brings Form 5471 every year. It can also push rental profit onto your personal return before any dividend reaches you. The British company structure has no American equivalent to shelter it.

Rental income is the sensitive part. Passive rental profit inside a CFC can reach the shareholder immediately. Actively managed property income can follow different rules.

Our guide to Form 5471 categories sets out the reporting that follows ownership of any British company.

The credit problem

Corporation tax paid by a British company is the company's tax, not yours. So it does not generally credit against your personal American tax on the same profit. You can end up taxed in America on income that has already suffered British corporation tax.

That mismatch is the core objection to incorporating while American. Before the company existed, British income tax on rental profit credited neatly against the American tax. Afterwards, it often does not.

Can an election fix it?

Sometimes. An entity election can make America treat the company as transparent, so the profits and the British tax flow through to you personally. That restores the credit and removes the CFC reporting.

The election has consequences. Making it after the company has traded can create a deemed liquidation for American purposes, with its own tax effects. Making it at formation is far cleaner.

Britain ignores the election entirely. The company remains a company here, paying corporation tax as normal, whatever America decides to call it.

A worked example

The figures below are illustrative. Take an example: an American landlord in Manchester owns six flats worth £1.8 million, bought for £1.1 million, producing £70,000 of rental profit a year.

Incorporation relief defers the £700,000 gain, which sounds decisive. But stamp duty on the transfer runs to roughly £150,000 unless partnership relief applies, payable in cash on completion.

Afterwards the company pays corporation tax on the rental profit. The American return may include the same profit, with no credit for the corporation tax, and Form 5471 arrives every year.

For this landlord, the American cost outweighs the British saving. A non-American landlord with the same portfolio might reach the opposite answer.

How do you get the money out?

Through salary, dividends or a loan account. Each has its own rate and its own timing. Dividends are the usual route, taxed on you after the company has already paid corporation tax.

For an American owner there is a second layer. The IRS taxes the dividend too. Credit is limited to the British tax you paid personally, not the tax the company paid.

So the combined rate can climb above what either country charges alone.

That is the trap. One tax, then another. Then a form each year.

How long until it pays for itself?

Often five to ten years. The stamp duty is the hurdle, because a large one-off charge takes many years of saving to recover. Add legal fees and higher lending rates, and the break-even point moves further out again.

Short horizons rarely work. If you may sell within a few years, incorporating usually costs more than it saves.

Sell soon and you lose. Hold for years and you may win. Time is the test.

When does incorporation still make sense?

Where the portfolio is genuinely a business. Where partnership relief removes the stamp duty. And where you settle the American position at formation rather than later. Landlords planning to retain profits in the company for reinvestment often benefit most.

It can also suit a couple where only one spouse is American, depending on who holds the shares. Model both systems together before anyone signs.

What about a partnership first?

Some landlords run the portfolio as a partnership before incorporating. Done properly, that can cut the stamp duty on the transfer. It also strengthens the business argument for incorporation relief, because a partnership shows the activity HMRC wants to see.

HMRC looks closely at these arrangements. A partnership formed a month before the transfer convinces nobody. Real partnerships have real history.

So plan early. Two or three years of genuine partnership records help far more than clever drafting.

Start early. Keep records. Show the work. Incorporation relief rewards a business that looks like one on paper as well as in practice.

Three questions to ask first

Is the portfolio a real business? Will the stamp duty bite? And are you American? Those three answers settle most cases, and the rest is detail.

Ask them before you ring a solicitor. They take an hour to answer. They can save a six-figure mistake.

We ask them in the first meeting. Often the answer is no. That saves the client more than any clever plan would.

How to test the plan properly

Run the numbers in both countries before the transfer, not after. Every step below is cheap in advance and expensive to unwind later.

1. Assess whether the portfolio is active enough to count as a business.
2. Value the properties and calculate the deferred gain incorporation relief would cover.
3. Quantify the stamp duty, including any additional and higher rates.
4. Check whether partnership relief is genuinely available on the facts.
5. Model the British tax before and after, including extraction of profits.
6. Model the American tax on the same profits, with and without an entity election.
7. Decide at formation how America should treat the company, then document it.

What about existing companies?

Americans who already own a British property company face the same questions in reverse. The reporting runs from the year the ownership began. Missed forms can usually come into a compliance programme, which beats fixing them quietly.

An election may still help going forward, but the deemed liquidation analysis matters. Take advice before filing anything, because the order of steps changes the outcome.

Mistakes and penalties we see with incorporation

• Assuming incorporation relief applies to any portfolio, without testing the activity level.
• Forgetting stamp duty on market value, which is payable in cash at completion.
• Incorporating while American without modelling the CFC rules.
• Missing Form 5471 in the first year, which keeps the whole return open.
• Making an entity election years later and triggering a deemed liquidation.
• Extracting profit as dividends without checking how America taxes them.

The British penalties here are ordinary. The American ones are not, because information return penalties start at $10,000 per form per year and apply whether or not tax was due.

So the order of work matters. Get the forms right first. Then look at the plan. Then sign.

How US UK Tax Accountants helps

We model the whole picture before you incorporate, including the stamp duty, the ongoing corporation tax and the American consequences. Where a company already exists, we bring the reporting up to date. If you are considering incorporating a portfolio, get in touch with the property details and we will run both sides alongside our UK Self Assessment work. Our guide to UK rental income on a US return covers the position before any company exists.

We start with the sums. Then the structure. Then the forms.

Last reviewed 23 September 2026. This article is general information and not personal tax advice. Reliefs, rates and surcharges change frequently, so take advice on your own portfolio before acting.