Overpay the mortgage, or pay into a pension?

Overpaying gives a predictable benefit: each pound repaid reduces the interest charged at your mortgage rate, with no investment risk. Whether that beats the alternative depends on the rates available, your tax position, how much access you need and any early repayment charges.

A pension works differently. Tax relief can significantly increase the amount invested, so a £1,000 gross contribution may cost a higher-rate taxpayer £600, subject to eligibility and how the relief is claimed. Salary sacrifice may add a National Insurance saving and an employer contribution can add more. Against that, investments can fall as well as rise, returns are not guaranteed, and the money is normally locked until the minimum pension age.

Which suits you is therefore subjective. It turns on your mortgage rate, tax position, contribution limits, employer contributions, timeframe, attitude to risk, how much accessible savings you need, and how much clearing the debt before retirement matters to you.

The calculator illustrates outcomes. It cannot tell you which is right, and it does not account for the annual allowance, emergency savings, early repayment charges, future tax on pension withdrawals, or what the money is ultimately for. Those are worth a conversation.