In the case of Spain, there is a tax called I.R.P.F. (Personal Income Tax), which self-employed individuals apply to their invoices. This tax is calculated based on the tax base and is subtracted. It is a negative tax. Currently GHL does not allow negative taxes to be added because it does not allow you to save the document, much less send it. For places where they have taxes as well as in Spain, it is interesting to have it enabled to be able to use the GHL bill part. thanks