Interest rate basis

The interest rate base is a basic notation on how an interest rate should be calculated against a customer. It is calculated by taking into account the number of days in a year. With a fixed interest rate, the interest is calculated taking into account that each month has 30 days i.e. 360/360. The calculation of the variable interest rate takes into account instead that a normal calendar base of a year, i.e. 366/365.9