The State Pension currently stands at £241.30 a week, or £12,547.60 a year. But it’s no secret that this alone isn’t enough to live even a moderately comfortable lifestyle in the UK today.

That’s why building a second pension income stream matters so much for people who want a far more financially secure retirement. And even earning enough to double the income from the State Pension alone is enough to have a significant positive impact on the quality of life.

So let’s say someone wants to earn another £12,547.60 a year once they decide to stop work? How big would a Stocks and Shares ISA portfolio actually need to be?

Crunching the numbers

Using the widely-followed 4% withdrawal rule, an ISA would need to be worth around £313,690 to comfortably generate that level of extra income each year.

Reaching this threshold sounds daunting at first glance. But it’s actually far more achievable than what most people think.

For example, let’s say a 44-year-old started a brand-new portfolio today and invested £500 each and every month at an 8% average return in line with the UK stock market. By the time they turn 65, their ISA would have grown to around £325,179. And by age 67, that number would have increased even higher to roughly £394,365.

Of course, the question now is, which UK stocks should they be considering?

A quiet compounder hiding in plain sight

One British business I’ve already added to my retirement portfolio is Diploma (LSE:DPLM). This is a business that rarely grabs headlines, yet it’s also one of the best-performing UK stocks of the last 20 years.

The group distributes specialised technical products, from seals and controls used in industrial machinery to life sciences components, acting as a trusted middleman between manufacturers and the businesses that depend on their products working reliably.

That ‘boring-but-essential’ positioning is precisely how Diploma has consistently outperformed. And looking at its latest results, that pattern hasn’t changed. Revenue climbed 17% to £851.1m, but the real story is where that growth came from. Organic sales alone grew 15%, meaning existing businesses are simply winning more work, not just buying growth through acquisitions.

Layer on 15 bolt-on acquisitions completed over the past year at disciplined valuations, and it’s easy to see why adjusted earnings per share surged 36% to 109.2p.

Where’s the risk?

Sadly, past performance isn’t an indicator for future results. And even Diploma has its weak spots. With acquisitions sitting at the heart of its long-term growth strategy, the company is exposed to considerable execution and integration risks that can quickly compromise the balance sheet if Diploma’s takeover engine starts misfiring.

After all, while Diploma’s a cash-generative enterprise, it still relies on debt to finance its bolt-on takeovers. And taking on new expensive debt to acquire an underperforming asset is a proven recipe to destroy shareholder value.

Nevertheless, in the case of Diploma, it’s a risk I’m happy to take. With a multi-decade track record of compounding growth, rising dividends, and expanding its market share, Diploma has already generated enormous wealth. And I remain optimistic that it has the potential to do it all over again.

Should you invest £5,000 in Diploma Plc right now?

When investing expert Mark Rogers and his team have a stock tip, it can pay to listen. After all, the flagship Twelfth Magpie Share Advisor newsletter he has run for nearly a decade has provided thousands of paying members with top stock recommendations from the UK and US markets.

And right now, Mark thinks there are 6 standout stocks that investors should consider buying. Want to see if Diploma Plc made the list?

 See The Six Stocks

Zaven Boyrazian owns shares in Diploma.

The post How much do you need in an ISA to match the £12,547.60 State Pension? appeared first on The Twelfth Magpie.

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