I’ve just uploaded a rough-and-ready program for modelling mortgage offsetting. Mortgage offset accounts are like savings accounts linked to a mortgage, but instead of earning interest they reduce the interest charged by offsetting the loan amount.
There are mortgage lenders that let you manage offset accounts on-line, and even show nice graphs to show the predicted effect of offsetting (i.e. how much less time it will take to pay off the mortgage) but this graph is a lot more configurable than any I’ve seen.
You can use it to say that you’ve a certain amount in the offset account, but you’ll be withdrawing an amount each month; or you expect a fixed term deposit to mature in 6 months; or there’s a big purchase on the horizon that will reduce the size of the offset.