Please

So I'm trying to set up a spread sheet A to check my mortgage statement is correct and B the effect of future over or under payments.

So the formula I used to calculate the daily interest is ((X/100)*interest rate)/365 and then add on the balance and minus my payments.

Thing is that by Dec 31st I'm like £5 out. So am I fucking up or are the bank screwing me over even further?

It's probably because you spelt the dollar sign wrong.

$

Mortgages are generally compounded continuously. Every month, your interest owed will be P*e^(rt). So that would be Amount Owed * e^((interest rate / 12)*(1 month)), or something like that. So if you owe 100,000 quid at 6%, your interest this month will be 100,000 * e^(0.06/12). Does that answer your question?

EDIT: The actual interest would be that amount minus the principle, so it'd be 100000 * e^(0.06/12) - 100000.

Over in 1.

also 365.25 days in a year

nice catch