Within each STEL Order invoice, you will have a field on the right hand side that says "Type of maturity", with a drop-down tab. When you click on the drop-down, it displays the types of maturities you have created. Select the one you need and at the top click Save.
The pdf that is generated from that invoice, will have at the bottom of the document a box with the type of due date chosen, date of each due date, amount and if it is paid or not. All the information that your customer needs to know in order to make the payments according to the maximum due date.