Per the IRS, a binding contract is evidenced by at least 5% non-refundable deposit.
https://rsmus.com/insights/tax-alerts/2022/irs-issues-guidance-on-transition-rules-for-ev-credits.html
There is also the possibility that the VIN must be on the contract.
Still awaiting IRS clarifications on...
Well to answer this forum's title, since I have a trimotor Cybertruck on order, I order the R1S as I need an SUV plus it looks like a Range Rover Land Rover.