A lump sum can reduce a mortgage, but the right choice is not automatic. Check the loan contract, any penalty or cashback clawback, your emergency cash and what the bank will recalculate.
Start with the contract
Ask the lender for the exact cost of a partial prepayment, minimum amount, notice period and whether you can keep the instalment or the remaining term. A quoted interest saving is incomplete until these costs are included. HKMA mortgage consumer information
Two useful choices
Keeping the monthly payment usually shortens the term and saves more total interest. Keeping the term normally lowers the payment and can improve monthly resilience. Neither is universally better: the first prioritises debt reduction; the second prioritises cash flow.
Do not use every dollar
Keep an emergency reserve and near-term essential spending outside the mortgage. Money paid into principal is not necessarily easy to access again. High-APR debt usually deserves attention before a low-rate mortgage.
Use the Mortgage Prepayment Calculator to compare both options, then deduct the lender-confirmed costs. If refinancing is also under consideration, compare cashback, legal costs and penalty terms with the Refinance Calculator.