from odoo import fields, models

class AccountTaxTemplate(models.Model):
    _inherit = 'account.tax.template'

    l10n_de_datev_code = fields.Char(size=2)

    def _get_tax_vals(self, company, tax_template_to_tax):
        vals = super(AccountTaxTemplate, self)._get_tax_vals(company, tax_template_to_tax)
        vals['l10n_de_datev_code'] = self.l10n_de_datev_code
        return vals

class AccountTax(models.Model):
    _inherit = "account.tax"

    l10n_de_datev_code = fields.Char(size=2, help="2 digits code use by Datev")