to give it to anyone. The law actually states the number is to be used for tax purposes only. It's not a general identity number that any business can choose to use. If this company is acting under order from the Federal Gov't to obtain tax id numbers from customers, they can legitimately ask, otherwise, tell them you'll give them an "ID" number and just make something up. If they insist on the real SS I'd either fake it or better yet, don't do business with them.