I asked ChatGPT if an ISA or SIPP was the best place to invest £10k this year and it said…

As the FTSE 100 booms, investors will be wondering whether to take advantage by investing in a Self-Invested Personal Pension (SIPP) or a Stocks and Shares ISA.

We Britons are lucky. Both are terrific tax-free ways to access the power of stock market investing, but offer slightly different benefits. So which is better?

It’s a tricky question, so I decided to call in artificial intelligence (AI), asking ChatGPT whether a SIPP or a ISA would make £10k work harder in 2026.

Two tax-efficient wrappers

The chatbot said the attraction of a SIPP is immediate. Contributions benefit from generous tax relief, so a basic-rate 20% taxpayer needs to invest only £8,000 to end up with £10,000 in their pot. Higher-rate taxpayers can claim another £2k back through their tax return. Better still, 25% can be taken as tax-free cash.

As ever, there’s a trade-off. Further SIPP withdrawals are taxed as income, and investors cannot access their money at all until age 55 (rising to 57 from 2028).

Please note that tax treatment depends on the individual circumstances of each client and may be subject to change in future. The content in this article is provided for information purposes only. It is not intended to be, neither does it constitute, any form of tax advice. Readers are responsible for carrying out their own due diligence and for obtaining professional advice before making any investment decisions.

Stocks and Shares ISA investments lack that upfront boost, but they’re more flexible. Withdrawals can be made at any age, and are always free of tax. Both wrappers shelter dividends and capital gains, allowing returns to compound quietly over time. Could combining the two be the smartest strategy?

ISAs are flexible

ChatGPT laid out the mechanics well enough but ultimately it’s a personal decision. Personally, I think these tax breaks complement each other nicely, and I would look to spread money between the two. That way investors get upfront tax relief from a SIPP, but can reduce their tax liability in retirement by making some withdrawals from an ISA.

For anyone investing £10k in 2026, it may be worth splitting contributions across both vehicles, or topping up the smaller one.

The next big question is which shares to buy? Here, I’d never ask ChatGPT to help me with that. It’s not a stock-picking programme, and is also prone to simple but potentially costly errors.

Games Workshop Group’s tempting

Investors seeking growth might consider Warhammer-maker Games Workshop Group (LSE: GAW). The miniature war games manufacturer fought its way into the FTSE 100 after a decade of spectacular gains. Last year, the shares climbed almost 40%, while over two years they’ve risen 95%. 

There’s income too. Games Workshop declared a 50p dividend on 17 December, taking total payouts for 2025/2026 to 375p per share, up from 265p in the previous 12 months. 

It’s a stock with momentum, but a word of warning: it’s not cheap. The price-to-earnings ratio now sits at 33.7, well above the FTSE 100 average of 17. Growth could be bumpy if profits disappoint or sentiment shifts.

Games Workshop has a massive growth opportunity through Warhammer’s upcoming streaming tie-in with Amazon. If that wins over audiences, Games Workshop could climb higher, but if diehard fans hate it, there could be a backlash. No stock’s without risk.

Momentum stocks like Games Workshop can be exciting, but investors need to balance them with holdings from other sectors, including dividend stocks, and invest for the long-term, not just 12 months. That applies whether they hold them in an ISA, a SIPP, or both.

The post I asked ChatGPT if an ISA or SIPP was the best place to invest £10k this year and it said… appeared first on The Motley Fool UK.

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• How much does one need in an ISA for £2,056 monthly passive income?
• £5,000 invested in this FTSE 100 stock at the start of 2025 is now worth over £7,500

Harvey Jones has no position in any of the shares mentioned. The Motley Fool UK has recommended Amazon and Games Workshop Group Plc. Views expressed on the companies mentioned in this article are those of the writer and therefore may differ from the official recommendations we make in our subscription services such as Share Advisor, Hidden Winners and Pro. Here at The Motley Fool we believe that considering a diverse range of insights makes us better investors.

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