Couples tax optimiser: is your money in the wrong name?

How the optimiser works

The tool above takes both partners' incomes, whether you are married or in a civil partnership, your household's annual savings interest and dividends, and where that money is currently held: all with the higher earner, split 50:50, or all with the lower earner. It then calculates the tax on those savings and dividends under each arrangement using full 2026/27 rates, checks your Marriage Allowance eligibility, and flags the Child Benefit position if you claim for children. The result is a single number: what the same money would save if it were held in the right name.

The reason a saving usually exists is that the UK taxes individuals, not households. Every allowance in the table below belongs to one person and cannot be pooled, so a couple who leave everything with the higher earner burn one whole set of allowances every single year.

The allowances each of you gets (2026/27)

The starting rate deserves a special mention because it is so poorly known. A partner with little or no other income can combine the £12,570 Personal Allowance, the £5,000 starting rate for savings and the £1,000 Personal Savings Allowance, making up to £18,570 of interest completely tax-free in their name. The same interest in a higher-rate partner's name is taxed at 40% after just £500.

A worked example

Alex earns £70,000 and pays higher-rate tax. Sam earns £20,000 and pays basic rate. The household has £2,000 a year of savings interest and £3,000 of dividends, all currently in Alex's name because the accounts predate the relationship.

• Interest, as things stand: Alex's PSA covers £500, leaving £1,500 taxed at 40%. Cost: £600 a year. Moved to Sam: £1,000 is covered by the PSA and £1,000 is taxed at 20%. Cost: £200. Saving: £400.
• Dividends, as things stand: £500 allowance, then £2,500 at 35.75%. Cost: £893.75. Moved to Sam: £500 allowance, then £2,500 at 10.75%. Cost: £268.75. Saving: £625.

Total: £1,025 a year, every year, for moving money between two people who share a mortgage anyway. Nothing here is a scheme or a loophole; it is simply using the allowances Parliament gave each of you. Run your dividend figures in detail with the dividend tax calculator.

Marriage Allowance and the Child Benefit angle

If one of you earns under £12,570 and the other pays basic rate, Marriage Allowance transfers £1,260 of the lower earner's Personal Allowance across, cutting the recipient's tax by £252 a year, with claims backdatable four years. Note the trap in the eligibility: the recipient must be a basic-rate taxpayer, so a higher-rate earner cannot receive it no matter how little their partner earns. Check eligibility and value with the Marriage Allowance calculator.

Child Benefit adds a second reason to care about which partner has the income. The High Income Child Benefit Charge is tested against the higher partner's individual adjusted net income between £60,000 and £80,000, not against your joint income. You cannot gift salary to each other, but the higher earner can reduce their adjusted net income with pension contributions, and investment income sitting in their name pushes it the wrong way. A household with two children has £2,337.40 a year of Child Benefit at stake; see where you stand with the Child Benefit tax calculator, and if pension contributions are the fix, the salary sacrifice calculator shows the mechanics.

Capital gains: the same trick on disposals

The optimiser focuses on yearly interest and dividends, but the identical logic applies when you sell something. Each of you has a £3,000 Capital Gains exempt amount for 2026/27, and gains above it are taxed at 18% for basic-rate taxpayers and 24% for higher-rate taxpayers. Because transfers between spouses and civil partners are no-gain, no-loss, you can move part of a shareholding to your partner before selling and legitimately use both exempt amounts and, where one of you pays basic rate, their lower CGT band too.

A quick illustration: Alex (higher rate) wants to sell shares standing at a £6,000 gain. Selling them all in Alex's name uses one £3,000 exemption and leaves £3,000 taxed at 24%, a £720 bill. Transferring half to Sam first means each sells a £3,000 gain, each covered in full by their own exemption, and the bill is zero. The transfer must happen before the sale and must be genuine, but for married couples it is explicitly how the rules are designed to work. The same planning applies to selling a rental property or a fund held outside an ISA, where the sums are usually far larger than £720.

The rules that keep it legal

• The gift must be real. HMRC's settlements rules ignore transfers where you keep control or an agreed right to take the money back. Move it properly: the account, the shares, the ownership.
• Spouses and civil partners transfer tax-free. Assets pass between you on a no-gain, no-loss basis with no Capital Gains Tax and no Inheritance Tax, which is what makes rebalancing so clean for married couples.
• Unmarried couples: gift cash, not grown assets. Transferring shares or property that have risen in value between unmarried partners is a disposal for CGT, with only the £3,000 exempt amount as cover. Cash gifts carry no such charge.
• Joint property has its own rules. Rental income between married joint owners is taxed 50:50 by default regardless of who paid for the property; changing that requires genuinely unequal beneficial ownership plus a Form 17 declaration, and possibly mortgage and stamp duty consequences. Take advice before touching property.

Common mistakes, and what to do next

• Optimising tax but ignoring the relationship risk. The money legally belongs to your partner afterwards, including on separation. Move amounts you are both genuinely comfortable with.
• Forgetting ISAs first. Interest and dividends inside an ISA are tax-free for either of you, so fill both partners' ISA allowances before optimising taxable accounts.
• Leaving it until the account matures. Interest is taxed on the person who owned the account when it arose, so rebalance before a fixed-rate bond pays out, not after.
• Set-and-forget. A pay rise that tips one of you into higher rate halves their PSA and raises their dividend rate overnight. Re-run the optimiser after any income change, and sanity-check the wider picture with the income tax calculator.

Start with the largest cash balance and the standing dividend payments, move them to the partner the tool recommends, then claim Marriage Allowance on GOV.UK if you qualify. An hour of admin, repeated savings every year after.

This tool gives estimates and general guidance, not personal tax advice; confirm the rules for your situation on GOV.UK before moving significant assets.