After non-payment of a Patent Issue Fee (being due three months after receipt of the USPTO Notice of Allowance) there is the option to file a Petition to Accept Late Payment of Issue Fee when non-payment was unintentional (37 CFR 1.137(a).
Is there a time limit in which the Petition to Accept Late Payment of Issue Fee needs to be filed ?
(The situation is similar to non-payment of maintenance fees. To my understanding (but this is not my question), here is a 24 months time limit after end of grace period for filing a petition to revive the patent when non-payment was unintentional.)