You can edit a vehicle's license plate in the TommyClub app when any of these is true:
The vehicle hasn't logged a wash yet.
The vehicle doesn't have an active plan.
It's been at least 30 days since you last edited the plate.
To update the plate:
Tap Vehicles, then tap the vehicle that needs a new plate.
Tap the pencil icon to edit the vehicle.
Tap the license plate field, enter the new plate exactly as it appears, then tap Save.
Your new plate shows on the vehicle. Tap the back arrow or Vehicles to return.
None of these apply to you? Add the vehicle again with its new plate, then transfer your plan to it. See Transferring a subscription for the steps.