The Driver and Vehicle Licensing Agency (DVLA) issues vehicle excise duty reminders to customers up to four weeks before the tax expires. The DVLA issues more than three million reminder letters each month. Complaints about non-delivery are rare, which suggests that the service works well for the majority of vehicle keepers. Occasionally vehicle keepers may not receive a reminder. This is often because the keeper may have moved house and not advised the DVLA of the new address, or the letter may have gone astray.