It has to do with the leases. If you just sell the car, then you record revenue in the amount of the sale * as soon as the buyer takes possession (typically this is a dealer, and the dealer takes possession when the car leaves the factory gate).
Since Tesla is doing their own lease transactions with a guaranteed repurchase price, the GAAP rules state the lease payments must be treated similar to rental income.
In the long term, it will balance out, but Tesla is providing non-GAAP accounting because changes to the lease/buy-outright mix will cause massive swings to the GAAP numbers, but that isn't really representative of the underling health of the company. The non-GAAP numbers basically assume all cars are bought outright.
Since Tesla is doing their own lease transactions with a guaranteed repurchase price, the GAAP rules state the lease payments must be treated similar to rental income.
In the long term, it will balance out, but Tesla is providing non-GAAP accounting because changes to the lease/buy-outright mix will cause massive swings to the GAAP numbers, but that isn't really representative of the underling health of the company. The non-GAAP numbers basically assume all cars are bought outright.
* less expected warranty cost.