Can I file a nonpublication request after submitting my patent application?

No, you cannot file a nonpublication request after submitting your patent application. According to MPEP 1122:

A nonpublication request must be filed upon the filing of the application. This is a statutory requirement and cannot be waived.

The request must be included with the application papers at the time of filing. It cannot be filed separately on the same date or at a later date. If you miss the opportunity to file a nonpublication request with your application, you cannot add it later.

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Tags: filing requirements, nonpublication request, USPTO