How to write tax amount to F0911 when processing a prepayment voucher

When processing a prepayment voucher the tax amount is zero on the R09801 and no amount is written to the F0911. How can I get the tax amount to show on the R09801 and write the tax amount to the F0911?

In the example above I would expect the debit side of the transaction to be 1000 to "PrePaid Services & Supplies" account and 200 to "Purchasing VAT" account