The good news- 4 out of 5 vehicles already meet the ULEZ emissions standards. Unsure if your vehicles meet the requirements, you can use the TFL vehicle checker.
If you vehicle does not meet the necessary requirements, you may consider other ways of meeting the standards such as replacing your vehicle, retrofitting your vehicle, Vans and diesel particulate filters or emission reduction technology. For more information: Ways to meet the LEZ standards – Transport for London (tfl.gov.uk)