In a Sales order, if I have a custom Transaction Line Field that is a field of type currency, is there a way to have it auto sum-up in the Subtotal lines, the same way that the

amount

field does?

Not natively. Custom currency transaction line fields don't automatically roll up into the Subtotal like the standard Amount field does. If your goal is to display or report a summed value, there are a few workarounds using SuiteScript, saved searches, or custom transaction forms. I've helped implement similar NetSuite customizations and would be happy to help you build the cleanest solution for your use case. @jen