There are two types of  self service “Machines” – CDM (Cash deposit machines) which are usually located in or just outside a branch.  These are online and would therefore reflect the payment on the same day but if you pay through an ATM (which is normally located in malls and public places), payments are only reflected the next day.  Be aware that if you are paying by cheque in any of the machines, it takes 3-4 days to clear.  So paying on the due date may still incur interest.