Can the filing of an inventor’s oath or declaration be postponed in a nonprovisional application?

Yes, for applications filed on or after September 16, 2012 (except reissue applications), the filing of an inventor’s oath or declaration can be postponed. The MPEP states:

For applications filed on or after September 16, 2012 (except reissue applications), applicant may postpone filing the inventor’s oath or declaration until the application is in condition for allowance if an application data sheet (ADS) in compliance with 37 CFR 1.76 is filed identifying: (1) each inventor by their legal name; and (2) for each inventor, a mailing address where the inventor customarily receives mail, and residence, if the inventor lives at a location which is different from where the inventor customarily receives mail.

However, the inventor’s oath or declaration must be filed no later than the date on which the issue fee is paid.