There's only a few days left to get major discounts on a Tesla Model 3 and 4 other EVs

• The federal EV tax credit rules are getting a major overhaul on January 1. 
• Discounts of $7,500 or $3,750 will soon be taken at purchase instead of later. 
• But these popular electric models may no longer be eligible. 

The rules for lucrative tax credits that can effectively lower the price of an electric vehicle by up to $7,500 will get stricter on January 1, meaning fewer vehicles will be eligible.

Popular vehicles like Tesla's Model 3 — one of the best-selling EVs in the US — and Ford's Mustang Mach-E, for example, will no longer qualify as new rules about where components are sourced kick in. Now, those with components made in China or from a Chinese-owned company no longer qualify, the Treasury Department said. 

Some manufacturers, like Tesla, have already warned their models will no longer be eligible. Others have said they're hopeful theirs still will, as the complex rules that confuse buyers also keep automakers scratching their heads. 

Of course, income rules and other pricing limits still apply, but the tax credit will soon be applied at the time of purchase to lower its price instead of retroactively at tax time.

Here's the list of models that may no longer qualify after January 1, leaving just a few days to get a discount: 

Tesla Model 3

Tesla preemptively warned that two versions of its Model 3 — rear-wheel drive and long-range—  will no longer be eligible, leaving only the most expensive option. Their batteries are produced in China at the company's Gigafactory near Shanghai. 

Ford Mustang Mach-E

Ford's electric Mustang Mach-E SUV will no longer qualify for the $3,750 half credit, Ford said in early December, offering no details on future eligibility or work to make the EV eligible.

Ford F-150 Lightning

As of its December statement, Ford was still reviewing if the electric F-150 Lightning pickup truck would qualify for tax breaks, Reuters reported. 

Cadillac Lyriq

General Motors expects its $57,590 Cadillac Lyriq to "temporarily lose eligibility," a spokesperson told The Detroit News.

Chevrolet Blazer EV

While it's currently not being sold due to software issues that left some drivers stranded, GM also expects the new Blazer EV to lose eligibility on January 1, pending supply-chain changes. 

The Chevy Bolt EV and EUV will remain eligible, the spokesperson said, as well as the electric Silverado Work Truck.