Importing VAT via iif files into QB Desktop

Can anyone help. I have simple bills (UK) with total amount, VAT and net amount. So far the only way that I've worked out how to bring the VAT amount into QB Desktop via the iif file is to have the total amount in the TRNS line and then two line items (SPL) - one with the net amount and the other with the VAT.....then import into QB Desktop and manually adjust the VAT code for the SPL with the net amount so that the VAT is automatically calculated, and then delete the second line item in QB that has the VAT code. This feels tortuous....the client will move to QB online in a few months but does anyone know an easier way to import total amount, net amount and VAT for a bill?

Thanks

Adam