Which of the following is NOT typically a requirement for enhanced emissions testing?

The requirement that is not typically necessary for enhanced emissions testing is proof of income. Enhanced emissions testing primarily focuses on ensuring that vehicles meet specific environmental standards, and the testing process is concerned with the vehicle's emissions output rather than the owner's financial situation or income level.

On the other hand, proof of vehicle registration is essential, as it verifies that the vehicle being tested is legally registered and complies with state regulations. Evidence of previous emissions test results may be required to establish a vehicle's history and ensure that it has been properly maintained or to determine if repeated testing is necessary. Valid identification is also important to confirm the identity of the vehicle owner and to enforce accountability during the emissions testing process. Therefore, while the other options relate directly to the requirements for emissions testing, proof of income does not.