If you forgot to renew your road tax, you should do it as soon as possible to avoid any legal consequences. You can renew your road tax online, by phone, or at a post office. The DVLA may issue a fine if your road tax has expired, but you can appeal if you have a valid reason for not renewing it on time. It is essential to keep your vehicle taxed and insured to avoid any legal consequences, and to set reminders for renewing your road tax and insurance to avoid forgetting in the future.