48 CFR §570.303-4

1. (a)If the Government's requirements change, either before or after receipt of proposals, issue an amendment. Document the amendment using the same method as for the SFO, written or electronic.
2. (b)If time is critical, you may provide information on SFO amendments orally.
   1. (1)Make a record of the information provided.
   2. (2)Provide, or attempt to provide, the notice to all offerors or prospective offerors on the same day.
   3. (3)Promptly confirm the information provided orally in a written amendment.
3. (c)Distribute an amendment as follows:
   1. (1)If before the proposal due date, send the amendment to all prospective offerors who were sent a copy of the SFO.
   2. (2)If after proposal receipt, send the amendment to each offeror who submitted a proposal.
4. (d)If an amendment is so substantial that it requires a complete revision of the SFO, cancel the SFO, readvertise if required by 570.106, and issue a new SFO.
5. (e)If there are changes to the Government's requirements for amount of space, delineated area, occupancy date, and/or other major aspects of the requirements, the contracting officer shall consider whether there is a need to readvertise, and to document the file accordingly.