This case be found by navigating to Transactions > Sales > Enter Sales Order. The two options will be available under the Billing tab.
A Sales Order can be created for either Cash Sale or Invoice Sale.
A customer may have a Credit Card saved in their record. When creating a sales order, under the Billing tab the preferred Credit Card details will be auto-populated under the "Payment" subtab. When the user enters a Term under "Billing Information" section, the Payment Method field will turn blank. If a payment method is selected, then the Term field will turn blank.
The reason behind is when a Term is selected, the system assumes that the sale will be an Invoice sale. If a Payment Method is selected, the system assumes that it will be a Cash Sale (which doesn't necessarily mean that it will be paid by cash but it will be paid upfront). Therefore, only one field must be filled and the other one must be blank.
Note: If Sales Order is for Invoice Sale, payment method can be selected upon accepting payment after having the Sales Order Billed.
If it is an Invoice Sale, all the credit card pre-populated information needs to be emptied before saving the sales order or else the system will ask you to select a Payment Method and if that is selected, the Term will turn blank.
This can also be avoided by customizing the Sales Order form and creating 2 separate Sales Order forms. One will be for Invoice Sales and one will be for Cash Sales. The Sales Order form for Invoice Sales can be customized to hide Payment subtab. The Sales Order form for Cash Sale can be customized to hide the Term field.
Note that is applicable assuming there is no preferred Term under Setup > Accounting > Accounting List. The behaviour is different when you have a preferred Term.
When there is preferred Term set under Setup > Accounting > Accounting List, both Payment Terms and Payment Method will be populated automatically. Upon saving the Sales Order, a pop up message will appear on the screen read as:
'This Sales Order has both terms and payment method set. When this is the case, payment method takes precedent, and a cash sale will be generated upon billing. To instead create an invoice, remove the payment method.'