[CKinPA]

Already seeing some effects of the Inflation Act signing. 2022 ID.4s sitting on dealer lots in larger numbers. And Tesla model 3s available for order as early as October 2022. I see a lot more cancellations of Tesla's and German ID.4s because they are directly affected by the new tax bill. Should be interesting how large inventory of ID.4s get before end of year and how quickly you can take order on a Tesla.

If you order a Tesla Model 3 in Dec. 2022... can you refuse to pick it up until January 1st and sign the paperwork then to get the possible $3750 or $7500 off?

We should always read the official guidance when possible. According to IRS.GOV:
Transition Rule for Vehicles Purchased before August 16, 2022
If you entered into a written binding contract to purchase a new qualifying electric vehicle before August 16, 2022, but do not take possession of the vehicle until on or after August 16, 2022 (for example, because the vehicle has not been delivered), you may claim the EV credit based on the rules that were in effect before August 16, 2022. The final assembly requirement does not apply before August 16, 2022.
Vehicles Purchased and Delivered between August 16, 2022 and December 31, 2022
If you purchase and take possession of a qualifying electric vehicle after August 16, 2022 and before January 1, 2023, aside from the final assembly requirement, the rules in effect before the enactment of the Inflation Reduction Act for the EV credit apply (including those involving the manufacturing caps on vehicles sold). If you entered into a written binding contract to purchase a new qualifying vehicle before August 16, 2022, see the rule above.
Source: Plug-in Electric Drive Vehicle Credit Section 30D | Internal Revenue Service (irs.gov)