In most cases your invoice will be paid 50 days from the end of the month in which you submitted your invoice. For example, if you submitted your invoice on the 28th August, it will be paid on the 20th October. You can view this Payment Due date on the Invoice History page.
Note that, if 50 days from the end of the month falls on a Saturday or Sunday, then the Payment Due date will be set to the next working day.