Allow Deductive Change/Credit to be billed when contract is at 100%

There needs to be a way for the system to allow for a credit to be billed for by the Sub even in the event it is their last billing.

if a subcontractor has billed 100% and their billings have been submitted previously and paid, it doesn’t seem the right protocol to unapprove an already approved invoice especially if it has been billed and paid.

ALSO and just as important, the ability to release the negative billing out of TP.