Doesn't matter what Tesla allows, it's what the
tax code says and what the IRS allows.
Given the way the tax code is written, I don't think payment matters, but rather when you start using the car.
Emphasis mine.
The
IRS interpretation leaves a little more wiggle room here though.
But I tend to view that as a backstop against creative interpretations of "placed in service" allowing credits for vehicles you don't actually own and not as an invitation to take the credit earlier based on titling the car before delivery.
Personally, I wouldn't risk trying to take the credit early. I'm not a tax lawyer or an accountant, so take my advice with a grain of sand.