can a passport be renewed after it expires
US DOS doesn't specify exactly but, if the passport is valid for 10 years and to renew it had to have been issues within 15 years of expiration. So, I am deducing it to be 5 years after expiration as long as you can send the original back with the application.
Passport Renewal. I f your US passport is expired, or will expire within the next 6-7 months, now is the time to renew it! If your passport is expired, you have 5 years from the date of expiration to renew it without going through the new passport procedure.