5 CFR 9801.106: Use and collection of social security numbers.

(a) No denial of right, benefit, or privilege. Individuals may not be denied any right, benefit, or privilege as a result of refusing to provide their social security numbers, unless the collection is required by Federal statute; and

(b) Notification to individual. Individuals requested to provide their social security numbers must be informed of:

(1) Whether providing social security numbers is mandatory or voluntary;

(2) The statutory or regulatory authority that authorizes the collection of social security numbers; and

(3) The uses that will be made of the numbers.