Many UK investors opt to invest via a Stocks and Shares ISA due to the favourable tax benefits. However, it may not necessarily be the best option.
Depending on individual needs, a Self-Invested Personal Pension (SIPP) could provide even greater benefits.
So what are the differences and, more importantly, what do the experts think?
Key differences
Essentially, SIPPs are designed with retirement in mind, while ISAs are for all types of savers. Investors aiming to save for a property or other large expense would benefit from the flexibility of an ISA. Those who are purely saving for retirement may prefer a SIPP.
SIPPs provide tax relief on contributions up to £60,000 a year and tax-free growth, but access is locked until age 55 (rising to 57 in 2028). Once retired, 25% of withdrawals are tax-free and the rest taxed as income.
Stocks and Shares ISAs have a £20,000 annual allowance, tax-free growth, no withdrawal costs and no access restrictions. This makes them better suited for medium-term goals.
Both allow investments in UK shares, funds, ETFs, and bonds, but SIPPs offer broader options like commercial property.
What the experts say
According to analysts at AJ Bell: “The two biggest differences are how and when you can access your money, and the tax relief bonus of a SIPP.“
SIPP Advice says: “In a nutshell, a SIPP is better for long-term savings, and an ISA is better for shorter-term savings.”
But according to some experts, a more effective approach may be using both options. “This gives you the best of both worlds: immediate tax benefits, long-term growth potential, and ultimate flexibility,” said an analyst at Freetrade.
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.
A stocks to consider
Legal & General (LSE: LGEN) stands out as a worthwhile dividend stock for UK investors building retirement pots via SIPPs or ISAs to think about. As a FTSE 100 life insurer and asset manager, it benefits from rock-solid income streams and defensive qualities.
Popular with income investors, its yield typically ranges between 8% and 9%. Payments are supported by stable annuity sales and pension risk transfer deals worth billions annually.
Dividend growth of 2%-4% is forecast, with low volatility suiting middle-aged savers eyeing passive income amid economic wobbles. At around 267p, it’s near 52-week highs but trades on a forward price-to-earnings (P/E) ratio of only 11 — suggesting decent value.
Over 20 years, investing £20,000 in L&G could highlight the SIPP edge. With an assumed 8% total annual return (9% yield plus modest growth, per forecasts), an ISA would grow to around £93,219 tax-free. A SIPP boosts the effective investment to £24,000 via 20% tax relief, reaching £95,084 net after withdrawal taxes (25% tax-free, 75% at 20%).
While the difference is minimal, a SIPP still comes out ahead by £1,865.
Final thoughts
The above example shows how investors with no need to touch their money until retirement could marginally benefit with a SIPP.
What’s ‘best’ depends very much on individual circumstances. However, in my opinion, the flexibility of an ISA makes it the preferable option. Even if you are investing for retirement, you never know when you might need cash in an emergency.
But don’t put everything in one stock – a diversified portfolio of stocks is a smart way to reduce risk, even if it brings down the average yield.

