I started my career as an actuarial student, and somewhere I still have my really scary textbook on actuarial mathematics — annuity pricing/amortization. A level payment fixed period annuity (e.g. mortgage) can be priced with any number of variables and the monthly payment (loan amount) will of course vary based on something as simple as whether the payment is made at the beginning, end, or middle of the month.
But your bank is usually not sitting around repricing your conventional mortgage (and on what date the interest due accrues) just because you sent them 2 checks instead of one WITHIN a given period.
Other types of loans, especially something like a line of credit with a recalculated daily balance, WOULD however benefit from multiple payments within a month.
But, now with electronic banking there is a bit more flexibility for regular mortgages. Chase for example allows you to make an online payment and specify either:
– pay your regular mortgage payment
– prepay a future regular mortgage payment
– pay additional principal within this period
