If you want to buy a Tesla and get the full tax credit, today is your last day to order for Tesla to guarantee delivery by December 31.

With the tick-over of the new year, the federal tax credits on Teslas will be reduced from $7,500 to $3,750.

That could raise base price of a Tesla from $39,700 after the tax credit to $43,450 (including delivery fee).  

DON'T MISS: Tesla sells 200,000th car, starting phaseout of federal tax credits

The order deadline to receive the full tax credit applies to any Tesla model, the Model S, Model X, or Model 3.

The federal tax credits were structured so that after any automaker sells 200,000 plug-in cars, the credits start a wind-down period. At that point, buyers can continue to claim the credit for the remainder of that quarter and for the full quarter following. After that, the credits are cut in half for six months, in half again for another six months, and get eliminated completely after that.

Tesla crossed the threshold last July, and the end of this year marks the last of its full credits.

CHECK OUT: Tesla sets Monday deadline for full tax credit

The company has joined forces with GM, Nissan, and other automakers, along with other electric-car advocates to lobby for the credits to be extended and restructured so they expire simultaneously for all automakers. That lobbying effort has just begun.

This is the second time Tesla has repeated the message that buyers have to order now to be guaranteed the full credit. On October 12, the company claimed they wouldn't guarantee that orders placed after October 15 would receive the credit.

Refuting that warning, the company sent out a notice just last week, setting today (Friday) as the new date, which the company confirmed today.

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The good news for Tesla and its fans is that this indicates the company has been able to produce cars more quickly than it anticipated in early October.

Many buyers have been able to buy Teslas directly from the company's inventory and take delivery in a matter of hours or days in the past several months. If you want the full tax credit, that option is likely to continue until near the end of the year. As long as buyers take delivery of their car by Dec. 31, the full tax credit applies. Pictures of lots overflowing with inventory around the country have become a fixture of Twitter and forums for weeks. Even so, based on deliveries, the Tesla Model 3 became the fifth bestselling sedan in the country in the third quarter.

Those who want to make custom selections from the options or color menu, however, need to do so today, the company says, or they could lose the full tax credit.

Truly, at some point, Tesla won't be able to fulfill a new order before Dec. 31. This might be that point, though it's hard to say for sure.