To apply interest to overdue accounts, go to Finance > Month End and Apply Interest in the top menu.  Select the month that you want to apply interest as of.  Interest will be applied for the last day of the month selected.   Month End Interest can be applied anytime within the last 5 days of the month* or later. 

The Interest Rate is the Global Interest Rate that is set up in Settings > Finance Settings.   By default, transactions will be charged interest when the transaction date is the month previous or older, except for when there is a due date beyond the interest applied date.       

You can click the View Interest Report to see which accounts will be applied interest and how much for the month.  

Return to Month End > Apply Interest for the same month and click Apply Interest for Period.  This will apply interest to all accounts in the report.  

An interest grace period has been added that will allow a few days grace when making payments.  For example, if the applied interest date is January 31st and the Interest Grace Period is 5 days, then payments can be processed without penalty up until February 5th.  The grace period will also allow for internal processing of customer payments in Sandbox.  Note: the date of generating the interest charges should be at least the applied interest date plus the grace period. 

Customers can be excluded from monthly interest charges by checking the "Don't Charge Interest" checkbox on the customer record.