Custom form/field anomalies or am I missing something?

Hi everyone,

A new subscriber to NetSuite here. While customizing NetSuite SB, I came across the following issues. Can someone enlighten me on the following. Would be much appreciated...

Transaction Body Fields:
After having created them, don’t show up in a given order in the actual forms (in the numbered sequence they show up in the Transaction Body Fields list).

I chose to put a custom field on “Payment” tab (seeing that “Payment” tab is an option to put the field on during field creation). But when I look in the appropriate form, there is no “Payment” tab. If the form (for example the Standard Service Invoice (where one would think the Payment tab should most appropriately show up) does not have a Payment tab, why is the option given in the Transaction Body Field creation section?