CRP20263
Debe haber sólo un registro por cada tipo de impuesto retenido (…).
In English A payment has one RetencionP per tax.
error: the document is invalid
What the rule checks
As the rule set's publisher wrote it. The rule runs on every element the context matches, and fails where the test is false; the validator reports the line of that element.
Context
pago20:ImpuestosP/pago20:RetencionesP/pago20:RetencionP
Test
count(../pago20:RetencionP[@ImpuestoP = $tax]) = 1
Checked with CFDI 4.0