Are you using the correct date convention? That can cause small differences in both the duration of the interest accrual period as well as the daily interest ra

Are you using the correct date convention? That can cause small differences in both the duration of the interest accrual period as well as the daily interest rate for that period If they aren't providing you complete information there is probably a Canadian authority you can reach out to, though you may just need to go higher up the food chain at your bank - accounting can be a little arcane and the people you are speaking to may simply not know. That being said being off by tens of dollars is absurd, the error is likely in your calculations, and I feel it is their duty to make how they calculate your interest owed plain to you.