The looming TikTok ban presents a multibillion-dollar headache for app store operators Apple and Google – as well as other Big Tech giants like Microsoft and Amazon that count its Chinese parent company ByteDance as a business partner.

The Biden administration effectively punted enforcement of the law, which is set to take effect on Sunday, to President-elect Donald Trump, who formally takes office the next day and has vowed to save the app.

On Friday, the Supreme Court rejected TikTok’s appeal and upheld the law, determining it does not violate the First Amendment.

Under the law, Google and Apple must stop allowing new downloads of TikTok – with potential fines of $5,000 per user if they don’t comply.

Sen. Tom Cotton – the outspoken Arkansas Republican who has supported the national ban – suggested that companies should be wary of ignoring the law even with assurances from key lawmakers that they won’t be on the hook for penalties.

“Penalties for companies like Apple and Google could run as high as $850 billion. Not sure I’d take a politician’s word if I ran those companies,” he wrote on X.

Aside from the immediate risks, Google and Apple will have to weigh the possibility that Trump or a future president could later decide to take action against them for failing to adhere to the law, experts told The Post.

Google declined to comment on its plans. Representatives for Apple did not respond to a request for comment.

The Supreme Court noted in its unanimous ruling that “Congress has determined that divestiture is necessary to address its well-supported national security concerns regarding TikTok’s data collection practices and relationship with a foreign adversary.”

Aside from the implications for Google and Apple, the Supreme Court’s decision adds fresh complications for Big Tech firms that have problematic “entanglements” with TikTok and ByteDance, according to Geoffrey Cain, policy director at the Tech Integrity Project and author of “The Perfect Police State.”

“Given the unanimous ruling that these Chinese firms are national security threats, it is time for Microsoft, Apple, Amazon and others to cut ties,” Cain told The Post.

In November, the House Select Committee on China blasted Amazon for entering a “dangerous and unwise” e-commerce partnership with TikTok.

TikTok is also one of the biggest customers for Microsoft’s cloud and AI services – and was paying nearly $20 million per month for access to OpenAI’s models through Microsoft as of last July, The Information reported. Microsoft previously faced heat for collaborating with ByteDance on an AI project called KubeRay.

Oracle provides cloud-computing support for TikTok and once partnered with the company on “Project Texas” – an ill-fated effort to convince lawmakers the app was safe from Chinese spying by storing all data for Americans on US soil.

Elsewhere, Reuters reported last month that Apple was in early talks with Chinese firms, including ByteDance, to roll out AI features in China.

Representatives for the House’s China select committee, TikTok, Amazon, Microsoft and Oracle did not immediately return requests for comment.

Should TikTok go dark, social media giants such as Facebook and Instagram parent Meta, Snap and Google-owned YouTube are in line to benefit from an influx of customers.

The law passed by Congress last April requires TikTok parent ByteDance to divest its stake entirely or face a ban on Jan. 19. The law allowed Biden to extend the deadline by 90 days if there were signs of progress toward a deal — but no such progress materialized.

Cotton noted those terms in his warning to the TikTok enablers.

“The only grounds for a 90-day extension are (a) significant progress (b) in binding legal agreements (c) to close a sale in 90 days. None of that has happened,” he wrote.

Trump is said to be mulling an executive order that would further delay enforcement of the law for 60 to 90 days while he attempts to facilitate a sale to a US buyer.

It’s not currently clear if an executive order of that kind would stand up to legal scrutiny.

TikTok is reportedly planning to take its app offline as the clock turns to midnight Sunday and redirect users to a website with details of the ban.

That move would go beyond the scope of Congress’s law, which requires only that app store providers like Google and Apple halt downloads.

The app would remain usable for a period for people who already downloaded it, but service would gradually degrade due to a lack of product support and updates.

TikTok CEO Shou Zi Chew is set to attend Trump’s inauguration on Monday and will be seated alongside other tech titans such as Elon Musk and Apple’s Tim Cook.