How do I check the interest on my overdraft?

Take each month's balance, the rate your agreement gives and the days in the month. Interest is the balance times the rate times the days, divided by 365. Compare that with the interest line on your statement. If the two differ month after month, the rate being applied is not the one in your agreement.

How the working goes

An overdraft is charged interest on what you owe, at a yearly rate, for the days you owe it. Your agreement usually fixes the rate as prime plus or minus a margin. When prime changes, your rate changes with it from that date.

Banks accrue on the daily balance. A statement usually shows only month-end figures, so the check uses the average of each month's opening and closing balance. That is a close approximation, not the bank's own daily sum, and the report says which basis it used.

Dividing the interest charged by the balance and the time it was owed gives the rate the charge works out to. Set beside the rate in your agreement, that is the plainest way to see whether the two agree.

Where Akurra fits

Akurra reads the margin and limit from your agreement, takes prime from the published series for each month, and does this sum for every month you have statements for. It shows what was charged, what the agreement gives, and the difference.