Will a Second Job Affect My Benefits?
Quick Answer
A second job's income can affect Universal Credit (reduced via the earnings taper), Child Benefit (if it pushes your individual income over the High Income Child Benefit Charge threshold), and student loan repayments (based on total income across all jobs). It generally doesn't affect your Personal Allowance itself, but the combined income from both jobs is what matters for these calculations.
Universal Credit
Universal Credit reduces by 55p for every £1 of net income you earn above your work allowance (if you have one, based on your circumstances). Income from a second job is added to your first job's income, and the taper applies to the combined total — so extra earnings from any job reduce your UC payment, though you always keep 45p of each additional £1 earned.
Child Benefit
The High Income Child Benefit Charge is assessed on individual adjusted net income, not household income. If a second job pushes your own income over the relevant threshold, some or all of your Child Benefit can be clawed back through the tax system. Check the current threshold on GOV.UK, as it's periodically reviewed.
Student Loan Repayments
Student loan repayments are calculated on total income above your plan's repayment threshold. If both jobs deduct student loan repayments separately through PAYE, you may end up overpaying during the year relative to your true combined-income liability — this is reconciled at year-end, often via Self Assessment if you also file a tax return.
Legacy Benefits
Working Tax Credit and Child Tax Credit have mostly been replaced by Universal Credit, but if you still receive them, additional income from a second job is assessed against your award in a similar way and can reduce it.