CMC Markets (LSE: CMCX) is easily the best performing FTSE 250 stock of the last 12 months, climbing an astonishing 231.57% in that time.

That’s the kind of performance we might expect from a US tech giant such as Nvidia, rather than a UK financial trading platform at a sketchy time for the FTSE.

To put that into perspective, the FTSE 250’s second best performer, TrustPilot Group, is up ‘just’ 142.72% over the last year, the laggard.

CMC Markets moves like Nvidia

Sadly, I don’t hold any of these three fliers, and I’m poorer as a result. But there’s an obvious danger in chasing past performance. So what are the chances of CMC jumping another 232% in the next 12 months? I’d say it’s limited by its very success.

With a market-cap of £875m, CMC does have room to grow. It doesn’t look too expensive despite its stellar success, with a price-to-earnings ratio of 18.98. That’s higher than the average FTSE 250 P/E of 11.1, but not out of sight.

A price-to-revenue ratio of 2.7% makes me wary. It means I’d have to pay £2.70 for each £1 of sales CMC makes. A price-to-book value of 2.2 is also on the high side.

Although a retail site, CMC is targeted at more sophisticated traders, specialising in contracts for difference (CFDs) and spread betting. It isn’t just a UK-focused operation, it has operations in Europe, Australia, New Zealand, Singapore and Canada.

A company like this thrives on stock market volatility, and with Donald Trump heading back to the White House, we’re likely to see a lot more of that. Yet the CMC share price hasn’t moved since the US presidential landslide, as many potential Trump trades have. That’s odd given that CMC offers crypto trading and Bitcoin’s going bananas.

It may have been knocked by domestic post-Budget worries. Or concerns over the impact of Trump tariffs on the non-US markets that CMC operates in.

CMC posted a blistering first-half update on 9 October, with net operating income up 45% to £180m as institutional business grew while operating costs fell.

The share price may have plateaued for now

CMC now anticipates that a £2m loss in the first half of the 2024 financial year will turn into a £51m profit before tax in H1 2025.

Trading platforms rely on clients making enough money to remain interested and active. It has an inevitable turnover as wannabe day traders try out spread betting and – like I did – discover it’s a great way of losing real money fast.

I’m therefore glad to see CMC targeting for both the institutional and business-to-business segment. It’s also looking to launch a cash ISA. That’s an odd decision but could offer a more stable revenue stream, albeit in a competitive market.

I’ll have a better idea of its staying power when CMC releases interim results on 21 November.

The four analysts offering one-year share targets have set a median price of 276.5p. If correct, that’s a drop of 11.74% from here.

That confirms my suspicions that I’m coming to this stock too late. Despite CMC’s relatively modest valuation, there’s a risk of a pullback. This is one for me to buy in a market crash, should we get one.