##### 7.1.4.2.5 Subject Registration Number Field __Certificate Field__: `subject:serialNumber` (OID: 2.5.4.5) __Required/Optional__: __Required__ __Contents__: For Private Organizations, this field MUST contain the Registration (or similar) Number assigned to the Subject by the Incorporating or Registration Agency in its Jurisdiction of Incorporation or Registration, as appropriate. If the Jurisdiction of Incorporation or Registration does not provide a Registration Number, then the date of Incorporation or Registration SHALL be entered into this field in any one of the common date formats. For Government Entities that do not have a Registration Number or readily verifiable date of creation, the CA SHALL enter appropriate language to indicate that the Subject is a Government Entity. For Business Entities, the Registration Number that was received by the Business Entity upon government registration SHALL be entered in this field. For those Business Entities that register with an Incorporating Agency or Registration Agency in a jurisdiction that does not issue numbers pursuant to government registration, the date of the registration SHALL be entered into this field in any one of the common date formats. Effective as of 1 October 2020, if the CA has disclosed a set of acceptable format or formats for Registration Numbers for the applicable Registration Agency or Incorporating Agency, as described in [Section 3.2.2.1.3](#32213-disclosure-of-verification-sources), the CA MUST ensure, prior to issuance, that the Registration Number is valid according to at least one currently disclosed format for that applicable Registration Agency or Incorporating agency.