FUNCTION ap-taxid-is-valid RETURNS LOGICAL
  (INPUT ip-taxid AS CHARACTER) FORWARD.
  

FUNCTION ap-taxid-is-valid RETURNS LOGICAL
  (INPUT ip-taxid AS CHARACTER):

  IF LENGTH(ip-taxid) = 10
    AND SUBSTRING(ip-taxid,3,1) = "-"
    AND TRIM(SUBSTRING(ip-taxid,1,2),"0123456789") = ""
    AND TRIM(SUBSTRING(ip-taxid,4,7),"0123456789") = ""
    THEN RETURN TRUE. /* EIN */

  IF LENGTH(ip-taxid) = 11
    AND SUBSTRING(ip-taxid,4,1) = "-"
    AND SUBSTRING(ip-taxid,7,1) = "-"
    AND TRIM(SUBSTRING(ip-taxid,1,3),"0123456789") = ""
    AND TRIM(SUBSTRING(ip-taxid,5,2),"0123456789") = ""
    AND TRIM(SUBSTRING(ip-taxid,8,4),"0123456789") = ""
    THEN RETURN TRUE. /* SSN or ITIN */

  RETURN FALSE.

END FUNCTION. /* ap-taxid-is-valid */