You can add VAT to non vatable disbursements, by following the steps below:
When posting your DUU (Disbursement Unpaid Unbilled) or DPU (Disbursement Paid Unbilled) do not apply VAT.
When raising your bill, Click Select Disbs and select the Disbursement, then click OK.
Double click on the Disbursement row on the bill posting screen, here you can now edit the VAT Code to apply VAT on billing, then click Save.