Guidance for Overlapping Certificate Revisions
This guidance applies only to DOE elements or persons working under contract to DOE elements
DOE elements means programs, operations offices, field/site offices, and other organizational units of the Department of Energy, excluding those of the National Nuclear Security Administration. The list of DOE elements is posted here. 
(link to DOE Directives website).
Only DOE elements or persons working under contract to DOE elements (i.e., contractors) shall consign a DOE certified package for shipment. NRC licensees or Agreement State licensees shall not consign a DOE certified package for shipment, but can transfer the material on-site to DOE elements or persons working under contract to DOE elements, for consignment of the package. See NRC legal interpretation: Transfer by an NRC Licensee of Radioactive Material or of Radioactive-Contaminated Facility Components to the Department of Energy 
(External link to NRC website)
The following guidance is based on DOE Packaging Certification Program consultation with NRC and DOT in 2017 and is consistent with how "overlapping" certificates are currently addressed and implemented by DOE, DOT, and NRC in their respective certificates.
Certificate Revisions of Type B or Fissile Packages certified by DOE
Certificates of Compliance (CoC) for transportation packages are revised periodically, for example, when the certificate is amended or renewed. The new, revised certificate supersedes the previous revision on the date of issue. However, this may cause compliance problems for shipments or shipping campaigns in progress on the date of issue. And for international shipments, the new certificate revision may need to be endorsed by the DOT or revalidated in foreign countries, adding scheduling difficulties. In addition, registered users of the CoC need time to implement the CoC revision in their operations procedures, if applicable.
The DOE (and NRC) recognizes these issues and the need for CoC revisions to overlap for a period of time, except in the following cases. No overlap period will be used:
• If the certificate is being revised to correct a safety problem or an error, or
• If the applicant requests that no overlap period is included.
DOE plans to limit the number of revisions that remain in effect at any one time, for consistency with NRC's practice. In general, only two revisions should be in effect at the same time. The previous revision will continue to be valid for a period of approximately one year, or until its expiration date, whichever occurs first. The overlap will be accomplished by including a condition in the new certificate revision that
authorizes use of the previous revision for a specific period of time. As shown in the example below, DOE will include an additional condition (Condition No. "X" in the example) on essentially all revised certificates. For purposes of this example, the new revision is Revision No. 2 and issued on September 30, 2017.
"X. Revision No. 1 of this certificate may be used until September 30, 2018."
Certificates Revisions issued by DOT
DOT certificates for transportation packages, special form radioactive materials, or uranium hexafluoride are revised when a certificate is amended or the expiration date is extended (i.e., renewed). DOT only supersedes previous certificate revisions to correct a safety problem or an error, or if specifically requested by the applicant; consequently, DOT does not limit of overlapping certificates like DOE or NRC. The new (i.e., latest), certificate does not supersede previous certificate(s), unless it's explicitly stated; otherwise previous certificates may be used until they expire.
Questions or comments? Contact the DOE Packaging Certification Program Manager, Dr. Shuler, (301) 903-5513,
james.shuler@em.doe.gov
Added September 26, 2017