The administrative penalty is $15 if plates are not renewed on time. You may renew online (https://mybmv.bmv.in.gov/bmv/mybmv/default.aspx), at a BMV Connect Kiosk (https://www.in.gov/bmv/branch-locations-and-hours/bmv-branch-map/), or visit a branch via walk-in service or a scheduled appointment (https://secure.in.gov/apps/waittimes/Schedule/Welcome.aspx).
Another option is to renew over the phone. If renewing your registration over the phone, you will need the access code provided on the registration renewal reminder notice you received in the mail.