A £50,000 ISA pot is a serious head start. But most people underestimate quite how serious. Invested thoughtfully, that sum has a realistic shot at generating £20,000 a year in passive income. Entirely tax-free, thanks to the ISA wrapper.

Let me show you the arithmetic.

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.

The maths

To produce £20,000 annually at a 6% income yield, I need a portfolio worth roughly £333,000. Starting from £50,000, that means growing the pot by just under seven times. Daunting on paper. Less so once compounding gets involved.

At the FTSE 100‘s historical average of around 7% annual total return, £50,000 reaches £333,000 in around 29 years. Respectable, but slow. Push that return to 10% — broadly in line with the S&P 500‘s long-run average — and the same target is hit in roughly 20 years.

Get stock selection right and compound at 12%, and you’re there in closer to 17.

That gap matters. Three years of additional compounding, at this scale, is the difference between tens of thousands of pounds in income. It also shows the importance of starting early. I started early in relative terms, but I certainly wish I squandered less of my first salaries and put just a few hundred pounds a month way.

Now, none of this is guaranteed. Markets don’t move in straight lines. They never will. What’s more, past returns are no promise of future ones. But the framework is sound. The ISA wrapper means the taxman takes nothing along the way — no dividend tax, no capital gains, no income tax on withdrawals.

The question is which stocks to buy?

Where to invest

There’s a rule of thumb I keep coming back to with airline stocks: the market prices them for catastrophe and forgets to reprice them when things go well. Jet2 (LSE:JET2) is a great example right now.

Adjust for the net cash — and this is a cash-generative business — and it’s a stock trading at roughly 4.2 times forward earnings. The sector average sits closer to 9.5 times. That’s not a small discount. It’s the kind of gap that tends to close, one way or another.

This is the type of investment I typically look for. I’m not betting on future performance or things picking up. I’m investing because the market’s overlooking the opportunity.

Operationally, the picture’s genuinely exciting. Revenue’s forecast to climb from £7.6bn in FY26 to £8.3bn in FY27, underpinned by fleet expansion and the addition of Gatwick. This is a move that meaningfully widens Jet2’s addressable market in the UK’s busiest aviation corridor. Near-term earnings are absorbing that investment — hence why earnings are sitting still this year.

Yes, UK unemployment‘s at a five-year high and fuel costs are structurally unpredictable. These are factors to watch. Likewise, the market may also be under-appreciating the positive impact motor finance payouts could have on the leisure travel sector.

However, at this price, I think the risk/reward is genuinely compelling. It’s worth considering.