On the invoice lines both taxes should be reported on sepate lines (tax authority cleary say that both amounts should be separated).
When posting the invoice normally both taxes are included on the same account.
For the VAT declaration both taxes are included on the same report (Modelo 303) but they are reported on diferent tax codes.
Because both taxes are related. We have 3kinds of VAT (normal, reduced and super reduced). And we also have 3 types of recargo (one for normal, one for reduced and another for super reduced).
Here are the types:
- Normal: IVA 21%, Recargo 5.2%
- Reduced: IVA 10%, Recargo 1.4%
- Super reduced: IVA 4%, Recargo: 0.5%
So if the supplier applies the Recargo tax, you should always include both taxes on the invoices and so on the report.
Here is another thread explaining the cases.