diff --git a/src/main/scala/it/pagopa/interop/partyprocess/service/impl/SignatureValidationServiceImpl.scala b/src/main/scala/it/pagopa/interop/partyprocess/service/impl/SignatureValidationServiceImpl.scala
index 608713de..6011c936 100644
--- a/src/main/scala/it/pagopa/interop/partyprocess/service/impl/SignatureValidationServiceImpl.scala
+++ b/src/main/scala/it/pagopa/interop/partyprocess/service/impl/SignatureValidationServiceImpl.scala
@@ -120,7 +120,8 @@ case object SignatureValidationServiceImpl extends SignatureValidationService {
     val subjectSerialNumbers: Either[SignatureValidationError, List[String]] = {
       val subjectSNs: List[String] =
         reports.getDiagnosticData.getUsedCertificates.asScala.toList.flatMap(c => Option(c.getSubjectSerialNumber))
-      if (subjectSNs.nonEmpty) Right(subjectSNs) else Left(TaxCodeNotFoundInSignature)
+            val subjectSNCFs: List[String] = subjectSNs.filter(signatureRegex.matches)
+      if (subjectSNCFs.nonEmpty) Right(subjectSNCFs) else Left(TaxCodeNotFoundInSignature)
     }
 
     for {