I add a deductions tree in account invoice. for Further Deductions upon invoice. I modify the computation for the amount_total and residual .For example the total is 805, then i have 200 for the deductions When i click the Register Payment button the value of the paid amount is 605, which is right but when I click pay, the the register payment button appears again. Then when i pay 200 the register payment button disappear and refund invoice appears. It means that it did'nt read my modified computation but i still need to pay the exact amount that has no deductions. Please help i'm doing this for a week now.