Interest is calculated daily and paid into your online account on the first working day of each month.
The interest owed to you per investment is calculated to 5 decimal places. As interest can only be paid out to 2 decimal places fractions of interest are accrued against every single investment. These are added together and are credited to your account each month.
You can download the detail of this interest payment from your account and can request to withdraw your available balance at any time.