When a proposal will not be funded, the PI generally receives written comments from all reviewers. Proposal resubmissions that are responsive to reviewers' critiques have a much higher likelihood of funding in a future cycle.
For one-time submissions, reviewer comments may also be useful for subsequent proposal development. The federal government is required to make review results available in a format of their choice (e.g., conference call, provide reviewer comments, a letter summarizing the comments). Private funding sources may not have the resources to provide feedback on a proposal and are not required to do so.
Upon being notified that a proposal will not be funded, the PI should forward a copy of the notification to the Pre-Award mailbox. The SPA database, SPAR, will be updated to reflect the status of this proposal.