<prompt> Human: First post to rpersonalfinance, but I felt this was the best sub to ask. Im a college student looking to build some credit, and Ive recently gotten a few letters from credit card companies about opening a card. Im thinking of going with Discover, and noticed in the application that a SSN is required at least I assume it is.Ive heard that when it comes to your SSN, you should only give it in certain situations such as schooling, taxes, hospital visits, and government institutions. I think Ive basically got three main questions:Why do they need it? What do they use it for if they have it? Should I supply it if I go through with the application, or is it optional?  <response>: Pretty much required. They need your credit report which is tied to your SSN. You have no choice but give it to them if you want to apply.But dont apply to the mailed card offers. Look on somewhere like nerdwallet.com for card offers. They tend to have better offers. 