In the event of a failed emissions test, what should the customer keep for reference?

Keeping the emissions test result is vital for several reasons. This document provides the official record of the vehicle's performance during the emissions testing process, showing whether the vehicle passed or failed the test. It outlines specific details such as the levels of emissions detected, any identified failures, and can also include recommendations for repairs if necessary.

Furthermore, having this result on hand is important for follow-up actions. If repairs are needed, this document serves as a reference point for mechanics or technicians to understand what issues need addressing. It may also be required for retesting, as the test facility may request to see the previous results in order to determine what repairs should be made and to track improvements.

The other options, while useful in their own right, do not provide the same level of specificity regarding the emissions test outcome. The initial invoice pertains to payment details, the vehicle registration is more about identifying the vehicle, and the technician's notes may contain helpful information, but they might not capture all necessary data from the official emissions test result.