Libro de IVA OSS

When you generate the Spanish VAT book, OSS (One Stop Shop) taxes are now handled properly. The module adds OSS taxes to the tax mapping used for the 'S_IVA' line, so they are recognised as part of the VAT book calculation.

During the calculation, any tax that is an OSS tax (a tax linked to an OSS country) is set to zero in the tax fee details. This prevents OSS amounts from being added to the domestic VAT totals, avoiding double taxation or incorrect figures.

The module works automatically in the background. It does not add new menus or screens; it only changes how the existing VAT book is computed. It affects the models account.move.line, aeat.vat.book.map.line, and l10n.es.vat.book.

• OSS taxes are included in the tax mapping for the S_IVA line.
• OSS tax amounts are zeroed out during the VAT book calculation.
• The VAT book calculation is run with a special context flag to activate this behaviour.

This is useful for Spanish companies that sell goods or services to other EU countries under the OSS scheme and need their VAT book to reflect only the correct domestic VAT amounts.