As a seller, the most important thing, aside from you, is a valid, non-expired, state or federal issued photo I.D., such as a passport or driver's license. It is also required to have one other validation I.D., such as a social security card, heath insurance card, voters' registration or birth certificate. You also need copies of your current tax, water, sewer bills if available. Don't forget keys to the house including the spare you gave your sister, garage door openers and any permanent documents useful to pass on the new owners.