Does a couple pay less tax if income is split between two earners instead of one?

Full answer

Because UK Income Tax and National Insurance are both progressive and calculated per individual (not per household), a household's total tax bill can differ significantly depending on how the same total income is distributed between two earners. Single earner on £70,000: taxable income of £57,430 gives £15,432 Income Tax (20% and 40% bands), plus £3,410.60 National Insurance, leaving £51,157.40 take-home. Two earners on £35,000 each (same £70,000 household total): each person's taxable income is £22,430, entirely within the 20% basic rate band, giving £4,486 Income Tax and £1,794.40 National Insurance each -- £6,280.40 combined deductions per person, £12,560.80 for the household -- leaving £57,439.40 combined take-home. The two-earner household keeps £6,282 more per year than the single-earner household on the same total income, because neither earner crosses into the 40% higher-rate band, whereas the single earner pays 40% tax on £19,730 of their income. This is a key reason why some couples structure family businesses, property income, or dividend income to split more evenly between partners where possible (subject to genuine ownership and HMRC's settlements legislation for arrangements between spouses), and why a stay-at-home parent returning to even a modest part-time income can meaningfully improve household after-tax income compared with one partner earning the full amount alone.

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