Let me reply your question in two parts:
The first question is really a very good one!
All the mortgage provider claimed they daily compund the mortgage charge. The formula will be:
PMT(Annual Rate/Calendar Days, Calendar Days, Capital)
Then it gives you the daily payment amount. You multiply it by 365 and divide it by 12 gives monthly amount.
I have to say I haven't tried and checked the above yet.
However, I compare the PMT monthly rate results with the actual mortgage, the result is nearly the same.
