5 CFR §9801.106

1. (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
2. (b)Notification to individual. Individuals requested to provide their social security numbers must be informed of:
   1. (1)Whether providing social security numbers is mandatory or voluntary;
   2. (2)The statutory or regulatory authority that authorizes the collection of social security numbers; and
   3. (3)The uses that will be made of the numbers.