Mortgage overpayments can reduce long-term borrowing costs, but the trade-off is reduced access to cash compared with holding savings or investments.
They reduce your balance faster, which reduces future interest because the mortgage is calculated on a lower remaining amount.
Many lenders allow annual overpayments up to a stated limit. Going above it can trigger early repayment charges.
The real question is whether overpaying beats your next best use of cash once risk and flexibility are considered.
Run your own scenario and compare one or two alternatives. That usually reveals the real decision much faster than generic advice.