Second jobs and multiple incomes

More and more people earn from more than one source — a second job, a weekend shift, freelance work alongside employment. It's a great way to boost income, but multiple incomes interact in ways that surprise people, mostly around tax. Understanding it stops the confusion and the unexpected bills.

The key idea is your tax-free personal allowance. You only get one, and it's usually applied to your main job. That means your second job is often taxed from the very first pound, with no tax-free slice of its own. This is completely normal and not a penalty — your allowance was already used against your main income — but it catches people out, who expect the second job to be taxed as lightly as the first.

It also matters whether your second income is employment or self-employment. A second employed job is taxed through PAYE like your first, just without the allowance. But genuinely self-employed side work — freelancing, selling, gig work — isn't taxed at source at all, so you're responsible for declaring it and paying the tax yourself through self-assessment. That's the one that most often leads to a surprise bill, because nothing is deducted as you earn.

Why this matters for you. When you add a second income, your overall tax picture changes, and looking at each job's payslip in isolation can mislead you. The smart move is to see your combined position — total income, total tax, real combined take-home — and to set money aside from any untaxed side earnings. mySal's jobs tracker and combined calculations are built exactly for people juggling more than one income.