Do 6%+ yields from SSE plc, Marks and Spencer Group plc and Carillion plc offer risk-free profits?

Thanks to the referendum, shares in utility group SSE (LSE: SSE) are worth 7.5% less than they were last Thursday. Yet this business isn't an obvious casualty of Brexit uncertainty.

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SSE issued a statement on Friday telling investors that UK's Brexit vote "presents no immediate risk" to the firm's operations or investment plans. Although the firm also warned that prolonged uncertainty could cause an increased level of risk, UK utilities have operated successfully in an uncertain environment for a number of years.

I hold SSE shares in my long-term income portfolio. Although there are no certainties in the current environment, I'm tempted to say that this stock is probably an attractive buy at the moment. SSE shares offer a forecast yield of 6.3% for this year and trade on 12.5 times forecast earnings. That's the cheapest they've been for some time. I'd be happy to buy more.

Is this 7.7% yield a buy?

Shares in support services firm Carillion (LSE: CLLN) are down by 8% as I write on Monday morning. The stock is now worth 20% less than it was at the start of the year. This sell-off has been driven by poor sentiment rather than downgrades to earnings forecasts.

As a result, Carillion shares now look very cheap, on a forecast P/E of 7.2 and with a prospective dividend yield of 7.7%.

One reason for this is that investors fear some big public-private infrastructure projects in which Carillion hopes to take part may be postponed following the referendum. This is possible, although it's not yet clear how or if the government's spending plans will change.

On the other hand, Carillion's historic operating margin of 5% is higher than that of its smaller peers. Net debt is relatively low at about £170m, or 1.3 times last year's after-tax profits. Although I'm nervous about the risk of cuts affecting Carillion's profits, I do think the shares could be worth a closer look at current prices.

Entering buy territory?

I expected Marks and Spencer Group (LSE: MKS) to fall further after May's annual results, but I didn't expect it to happen this fast.

M&S shares are now worth 22% less than one month ago. They've fallen by 45% over the last year. Although the group does face some challenges, it was still profitable and cash generative last year. The stock's trailing dividend of 18.9p per share now equates to a 6.3% yield. If it's sustainable, that's very attractive.

One concern I have is that Marks and Spencer's net debt is probably a little higher than it should be. Net debt was £2.14bn at the start of April, which is between four and five times the group's after-tax profits in recent years. That's quite high.

In May's results, Steve Rowe, M&S's new chief executive, said that trading conditions were "difficult". Mr Rowe said that turning around the firm's struggling clothing division "will have an adverse effect on profit in the short term".

I think it may be too soon to buy into the M&S turnaround story. Broker forecasts for this year's earnings have been cut by 12% since April. I suspect they could fall further, so I'm not buying M&S at the moment.

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Roland Head owns shares of SSE. The Motley Fool UK has no position in any of the shares mentioned. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.