Compare the numbers before making extra mortgage repayments
Paying down debt saves interest at the mortgage rate. Compare that with the reliable after-tax return available elsewhere. The source favors repayment if the alternative is lower or uncertain, after preserving emergency cash. Earlier repayment saves more total future interest; the bank app's prepayment calculator can show the amount.
What it takes
Free, around half an hour to calculate. Be honest about the stable after-tax return you could otherwise obtain.
What you may gain
Let r be the annual mortgage rate in your contract. China's over-five-year LPR on August 20, 2026 was 3.5%; actual mortgage rates add or subtract a contractual spread. Let g be the alternative annualized after-tax investment return. Prepayment gives a certain interest saving at r. If g reliably exceeds r, the alternative is financially preferable; if g is lower or uncertain, repayment locks in the avoided interest. With equal principal-and-interest payments, interest makes up a larger share early on, and earlier repayment saves more future interest. Use the lender's prepayment calculation for your own numbers.
Context & considerations
This provides a method, not an individual verdict. Reliably beating the mortgage rate is uncommon. Preserve adequate emergency liquidity either way and check contractual prepayment penalties. This is not investment advice.
Research & references
National Interbank Funding Center, authorized by the People's Bank of China (2026). August 20, 2026 Loan Prime Rate announcement. https://www.chinamoney.com.cn/chinese/rdgz/20260820/3399885.html