[FIX] l10n_it_fatturapa_out: fix issue OCA#3670

fix case use downpayment on e-invoice

Co-authored-by: Marcoapu <m.cazzato@apuliasoftware.it>

l10n_it_fatturapa_out/wizard/wizard_export_fatturapa.py

@@ -13,6 +13,7 @@
 
 from odoo import api, fields, models
 from odoo.exceptions import UserError
+from odoo.tools import float_is_zero
 from odoo.tools.translate import _
 
 from odoo.addons.l10n_it_account.tools.account_tools import encode_for_export
@@ -136,12 +137,21 @@ def _key(tax_id):
             tax_line_id = tax_id.tax_line_id
             aliquota = format_numbers(tax_line_id.amount)
             key = _key(tax_line_id)
+            tax_amount = 0
+            dp = self.env["decimal.precision"].precision_get("Account")
+            if invoice.move_type == "out_invoice":
+                if float_is_zero(tax_id.credit, dp) and tax_id.debit:
+                    tax_amount = -tax_id.balance
+                if tax_id.credit and float_is_zero(tax_id.debit, dp):
+                    tax_amount = abs(tax_id.balance)
+            else:
+                tax_amount = abs(tax_id.balance)
             out_computed[key] = {
                 "AliquotaIVA": aliquota,
                 "Natura": tax_line_id.kind_id.code,
                 # 'Arrotondamento':'',
                 "ImponibileImporto": tax_id.tax_base_amount,
-                "Imposta": tax_id.price_total,
+                "Imposta": tax_amount,
                 "EsigibilitaIVA": tax_line_id.payability,
             }
             if tax_line_id.law_reference: