If you mortgage lender calculates interest on a daily basis then, yes, this could yield significant savings. If they calculate interest less frequently than this (e.g. weekly (?), monthly, annually) then there is nothing to be gained by making repayments more reqularly than the interest calculation period. Not sure if any lenders would facilitate daily as opposed to weekly etc. repayments and they might be more inclined to steer the borrower towards a current account/offset mortgage if they offer such a thing and which does more or less the same thing as daily repayments (watch that this type or mortgage doesn't charge a higher rate than normal though). Hope that makes sense!