The quote validity and payment/ delivery terms drop-down boxes have a set of options for you to choose from at the bottom of the Quote Create window.
You can customise your own payment and delivery terms by selecting the “custom” option in the respective drop down box.
Once you select the custom option, “payment Date” box appears next to the Payment Terms box. Click on the calendar icon (as shown in the following picture) and set the required date. You can customise your “Quote Validity” options and “Delivery Terms” in the same manner.