Anthropic will list on the Nasdaq on 19 November at a target valuation of $1.4 trillion (£1.1 trillion), and several of the UK's largest investment platforms have already begun accepting retail orders for the shares, according to the company's latest filings.

The float is set to be one of the biggest IPOs of all time. Investment bankers are weighing plans to raise the offer price after heavy investor demand, according to reports.

London-based fintech RetailBook will co-ordinate the UK retail offer. Anthropic is issuing 825,000,000 shares at an estimated $70 to $78 per share, with 20 per cent of the offer reserved for retail investors. The number of shares allocated to the UK is unconfirmed. Investors have until 18 November to purchase.

Which platforms are taking part?

Seven platforms are participating in the share sale:

• AJ Bell
• Hargreaves Lansdown
• Robinhood
• Interactive Investor
• Interactive Brokers
• Revolut
• Etoro

Minimum investment requirements differ sharply. Hargreaves Lansdown has set a floor of £250 per client; AJ Bell requires £1,000 per investor.

How can UK retail investors access a US IPO?

Under standard US listing rules, IPOs are off-limits to international retail investors. Anthropic is using the Financial Conduct Authority's public offer platform (POP) regime to grant UK investors access — the same route SpaceX used in its blockbuster June IPO, the first under the regime.

Several platforms cited the SpaceX precedent. More than 100,000 UK investors applied for almost $1bn of the space technology firm's stock. Some received allocations worth as much as $135,000, while others missed out on their full applications amid the surge in interest. Those who got shares benefited from a 19.2 per cent first-day pop. Despite a post-IPO tumble, SpaceX remains one of the most popular stock holdings among UK investors.

Simon Belsham, chief client officer at Hargreaves Lansdown, said: "Companies sell shares to institutions globally when they go public, and with new technology and regulation, it makes little sense to leave out retail investors."

"As demonstrated by SpaceX, opening IPOs to individual investors worldwide gives companies a deeper, more diverse pool of demand, and gives… clients the chance to invest at the offer price and become owners from day one."

Hargreaves Lansdown clients accounted for roughly half the demand for SpaceX's UK debut, and 73 per cent still hold their shares after six months, the firm said.

Will demand hold after the tech sell-off?

The share sale comes despite last week's mass tech sell-off, which wiped $2.5 trillion off the Nasdaq Composite index on Thursday alone.

Some market analysts believe the slide in the broader AI sector, coupled with Anthropic's valuation coming in below earlier estimates of $2 trillion, may weigh on UK investor demand.

David Morrison, senior market analyst at Trade Nation, said: "The fact that [Anthropic] have said forget about $2 trillion… we know that's not realistic anymore but we're still going ahead."

"Is that quite positive or is it absolutely desperate? And is this their last chance to get some money before another serious implosion?"

Is a leveraged bet on the table?

For investors with a high appetite for risk, Leveraged Shares plans to list a 3x Long Anthropic exchange-traded product on the London Stock Exchange ahead of the IPO. The vehicle will hold cash until Anthropic actually floats, giving UK traders a leveraged position from the first day of trading.

The orders window closes on 18 November; the verdict on the $1.4 trillion price arrives the next morning in New York.

By Elena Vasquez