The £100,000 Tax Trap: Why Property Income Can Cost You 60p in the Pound

We see this catch out landlords who never thought of themselves as higher earners. Someone with a decent salary, a portfolio bringing in steady rental profit, no exotic planning anywhere in sight, and yet their accountant tells them a chunk of last year's income was taxed at 60%. Not 45%, the additional rate people worry about. Sixty. It isn't a mistake and it isn't a special rate for landlords. It's the personal allowance taper, and property income is one of the most common ways people wander into it without realising.

The mechanics of the taper

Everyone gets a personal allowance, currently £12,570, that's free of Income Tax. Once your adjusted net income passes £100,000, that allowance starts being withdrawn at a rate of £1 for every £2 of income above the threshold. By the time income reaches £125,140, the allowance has gone completely, and every pound above that is taxed as if you'd never had one.

Adjusted net income is your total taxable income, salary, rental profit, dividends, savings interest, before personal allowances are deducted, but after certain reliefs like pension contributions and Gift Aid. It isn't limited to employment income. If you're a landlord with a job and a portfolio, both feed into the same number.

Why the 60% figure is real, not a rounding trick

Take a pound of income that falls inside the £100,000 to £125,140 band. At higher rate, that pound is taxed at 40%, leaving you 60p. But because you earned it, you've also just lost 50p of personal allowance that would otherwise have been tax-free. That 50p of allowance, now taxable at 40%, costs you a further 20p. Add the two together and a single pound of income inside the band costs you 60p in tax, an effective marginal rate of 60%, even though no such rate appears anywhere in the official tax tables.

It's worse again for anyone with student loan repayments still running, or for someone who also loses eligibility for tax-free childcare or 30 hours of free childcare once income tips over £100,000, both of which are cliff-edge losses rather than tapered ones. The personal allowance taper on its own is bad enough. Stacked with those other thresholds, the effective cost of earning that next pound can be considerably higher still.

Why property income makes this worse than salary alone

A salaried employee usually has some visibility over what they're going to earn in a tax year. A landlord doesn't always have the same clarity. Rental profit moves with occupancy, with a mortgage renewal that resets the interest cost, with a year where several properties need work done at once versus a quiet year with none. Because Section 24 has removed mortgage interest as a deductible expense for individual landlords, and replaced it with a basic rate tax credit instead, gross rental income can push adjusted net income up even in a year where the actual cash profit after finance costs was modest. That's a common trap in its own right, and it interacts directly with the taper: the way Section 24 is calculated means a landlord's taxable rental profit can be significantly higher than what actually reached their bank account, and it's that higher figure that counts toward the £100,000 threshold.

Add a spouse or partner already earning close to six figures from employment, and a portfolio held in joint names can tip both of you into the band at once through what looks like a fairly ordinary year of rental income.

What actually reduces the bill

• Pension contributions. A relief-at-source or salary sacrifice contribution reduces adjusted net income pound for pound. For someone sitting just inside the £100,000 to £125,140 band, a contribution large enough to bring income back under £100,000 restores the full personal allowance, on top of the usual higher rate relief on the contribution itself. This is usually the most powerful and most straightforward lever available, subject to the annual allowance and how much of it remains unused from the last three tax years.
• Gift Aid. Charitable donations under Gift Aid also reduce adjusted net income, on the same basis as pension contributions, though the sums involved are rarely large enough to move the needle as far.
• Timing of income where there's genuine flexibility. A landlord with some control over when a large repair is incurred, or when a fixed-term tenancy renewal lands, may be able to smooth taxable profit across two tax years rather than concentrating it in one, keeping both years further from the threshold. This only works where the timing reflects something real, not an artificial deferral.
• Reviewing how the portfolio is held. Where a property is held jointly between spouses or civil partners, a Form 17 election alongside a declaration of trust can shift the split of rental income toward whichever partner has more headroom below £100,000, rather than the default 50/50 split that applies automatically to jointly owned property.

Where a company structure changes the picture

The taper only looks at income that reaches your personal tax return. Profit sitting inside a limited company isn't counted at all until it's paid out as salary or dividends. For a landlord whose personal income is already close to £100,000 from employment or other sources, holding new acquisitions through a company, or leaving profit inside an existing one rather than extracting it every year, keeps that income out of the taper calculation entirely. It doesn't make the tax disappear, corporation tax and eventually extraction tax still apply, but it stops rental profit from being the thing that drags your personal income across the threshold. Whether that trade-off is worth it depends on the wider picture, including the loss of certain personal reliefs and the different treatment on an eventual sale, so it's worth working through properly rather than assuming a company is automatically the answer. See how personal and company ownership actually compare before deciding.

Common mistakes

• Assuming the taper only applies to salary, and not checking whether rental profit and dividends push adjusted net income over £100,000
• Using gross rental income as a mental proxy for what's taxable, when Section 24's finance cost restriction can leave taxable profit well above actual cash profit
• Missing the pension contribution window before the end of the tax year, when it's the single most effective way to pull income back under the threshold
• Leaving jointly owned rental property on the default 50/50 income split when one partner has far more headroom below £100,000 than the other
• Not checking the combined effect with student loan repayments or the loss of free childcare, which can make the real cost of crossing £100,000 higher than the personal allowance taper alone suggests

What actually protects you

Know where your adjusted net income is likely to land before the tax year ends, not after, because most of the tools that help, pension contributions, Form 17 elections, timing decisions, only work if there's still time to act. If a portfolio is approaching the point where rental profit alone is enough to push combined income past £100,000, it's worth modelling the actual marginal rate rather than assuming the headline higher rate band tells the full story.

Common questions

What is the personal allowance taper and who does it affect?

It's the withdrawal of the tax-free personal allowance for anyone with adjusted net income over £100,000. The allowance reduces by £1 for every £2 of income above that threshold, disappearing entirely once income reaches £125,140. It affects anyone whose total taxable income, including rental profit, dividends and salary, falls in that band.

How does rental income push someone into the 60% tax band?

Rental profit is added to your other taxable income to work out adjusted net income. If a landlord's salary and other income already sit near £100,000, even a modest amount of property profit on top is taxed at 40%, then triggers the loss of £1 of personal allowance for every £2 earned, which pulls a further slice of income into tax that would otherwise have been free. The combined effect is an effective marginal rate of 60% on income within the band.

Can pension contributions fix the personal allowance trap?

A relief-at-source or salary sacrifice pension contribution reduces adjusted net income pound for pound, so it can pull income back under £100,000 and restore some or all of the personal allowance. This is usually the single most effective lever available, though it only works for income within scope of relievable pension contributions and is subject to the annual allowance.

Does the taper apply if property income is earned through a limited company?

Not directly. The taper is a personal Income Tax mechanism and only looks at income that lands on your personal tax return. Profit retained inside a property company isn't counted until it's extracted as salary or dividends. That's one of the reasons landlords holding portfolios personally and approaching £100,000 of other income often look again at whether a company structure suits them better.

This article is general information, not personal tax advice, and tax rules change. Your own position depends on facts we cannot see from here — please take advice before acting on anything above.

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