There are some different provisions by year, and for the signed sale contract.

Are you using the IRS resources available on the web?

2023: https://www.irs.gov/credits-deductions/manufacturers-and-models-for-new-qualified-clean-vehicles-pur...

2022: https://www.irs.gov/credits-deductions/manufacturers-and-models-for-new-qualified-clean-vehicles-pur...

You need to evaluate if each purchase qualifies and what it qualifies for and which tax year applies.