Yes, you can update your Caste Validity Certificate number. In fact, you must update it to the new format to claim reserved category benefits during the final admission (CAP) process.

The MHT CET 2026 application form will have a "Correction Window" (expected in March). You can log in and edit document details, including uploaded document numbers, during this time. Here is more about that - https://engineering.careers360.com/articles/mht-cet-application-form-correction