Research products falling under the policy must be submitted to the repository NSF-PAR (NSF Public Access Repository) before they can be included in NSF project reports.
The NSF's public access policy applies to research resulting from awards submitted or due after the effective date of January 25, 2016.
Research Products that Fall Under the Policy
Note: If you are familiar with the NIH Policy, this is a departure in that conference proceedings are included under NSF's, though not under NIH's policy.
Timeline for Compliance
The article or proceeding must be in compliance by the time a project report is submitted or it can not be included in the report. You can submit the manuscript to NSF-PAR while compiling the report. NSF indicates that, after deposit, the process of validation will take no longer than six hours.
There is a publisher-determined "administrative period" (embargo) of up to 12 months that applies to deposited works. NSF (with publishers) seems to handle determining and managing this period. You will not be asked to report this.
What Version to Submit
You must submit a PDF/A version of the paper, either way.
The version submitted may or may not be the one made available to the public, depending on publisher policies. It WILL be available to PIs, Co-PIs, and NSF Program Staff after the project report is submitted.
How to Deposit
Manuscripts must be submitted to NSF-PAR through the Research.gov site. Only the PI or co-PI can submit materials to NSF-PAR.
Submission can be done from Research.gov in two ways