Can I add a priority claim to a patent after it has been issued?

Yes, it is possible to add a priority claim to a patent after it has been issued, but the process requires filing a reissue application. The MPEP states:

‘A reissue application can be filed to correct the failure to adequately claim priority under 35 U.S.C. 119(a)-(d) or (f) or 35 U.S.C. 120 in the issued patent.’

To add a priority claim, you would need to:

• File a reissue application under 35 U.S.C. 251
• Amend the specification to include the required reference
• Ensure the reissue application is filed within the time period set forth in 35 U.S.C. 119(a)-(d) or (f)

It’s important to note that adding a priority claim may affect the patent’s term and could potentially impact its validity if prior art emerges between the new priority date and the original filing date.