Can I Hold Individual Time Entries?

In Bill Prep, remove the check mark from the Bill field on the Fee transaction you do not want to be billed on the Invoice - this will defer that individual transaction from billing.  You can replace the check mark in that field the next time you do billing or whenever you decide you want to bill that individual transaction.  As for changing the status of a transaction from billed to unbilled, you must unpost and void the Invoice.