After an invoice proposal is created, users can click the posted sales tax button to calculate and view the sales tax amounts related to a project invoice proposal. Because the sales tax value isn't calculated on project invoice proposal creation, it cannot be reviewed through the project invoice proposal listpage (as is possible on the project invoices listpage). The project invoice proposal table (ProjProposalJour) has a field for sales tax (sumtax), but its value never updates for the project invoice proposal.