LONDON -- As May arrives, we're moving into full-year reporting season for companies whose financial years end on March 31 -- and that includes a number of our best-loved FTSE 100 firms. We will actually have full-year figures from several of them next week, but we'll take a look at those later this week. Today, we'll look at five key results coming our way over the rest of May:

Thursday, May 16: National Grid (NG 1.68%)
Electricity and gas supplier National Grid will report on its full year on May 16. The key figure for cash-cow investments like this is the dividend, though the share price has risen by 23% over the past 12 months to today's 814 pence, boosted by strong interim results.

A year ago, shareholders enjoyed a dividend yield of 6.2% based on the end-of-year share price. We should be expecting to see a rise in the payment of about 4.5% based on City forecasts -- though the share price appreciation does drop the prospective yield to about 5%. That's still pretty good, considering that utility company dividends are among the safest in the FTSE.

Tuesday, May 21: Marks & Spencer (MKS 0.85%)
It's reckoning time for Marks & Spencer on May 21, when we'll hear how the latest chapter in the high-street chain's recovery story has ended. This month's fourth-quarter update told of the "strongest quarterly sales growth in the last two years," with overall group sales up 3.1%. U.K. sales were led by food, though, with general merchandise declining.

Current forecasts suggest a fall in earnings per share of about 8% and a dividend yield of 4%, based on the current share price of 411 pence. And at this stage it would be surprising if that were not close to the truth, especially after the Q4 update told us, "We continue to make good progress in transforming Marks & Spencer from a traditional U.K. retailer to an international multi-channel retailer."

Tuesday, May 21: Vodafone (VOD -0.15%)
The same day will bring us annual results from Vodafone, and barring any last-minute surprises, we should be seeing a dividend yield of about 5%. Even after the recent share-price rise to 197 pence, that's still a decent yield. February's update for the quarter ending Dec. 31 revealed mixed figures, including a services revenue fall countered by a rise in data revenues, coupled with tough conditions in Europe but growth in emerging markets.

But the elephant is the on-again/off-again mooted merger with U.S. telecom giant Verizon Communications, which raised its head again this week. Whatever eventually happens, investors will be looking for clues about Vodafone's plans for its 45% stake in Verizon Wireless.

Thursday, May 23: SABMiller (LSE: SAB)
How many shares have beaten the FTSE for 12 years in a row? The only one I know is brewer SABMiller, and so far this year it's on track to do it for a 13th year. The price stands at 3,481 pence now, having gained more than 30% over the past 12 months, and it may well get a further boost from annual results expected on May 23. And things are going in line with expectations after the maker of Grolsch and Coors, among more than 200 different brews, announced a 10% rise in full-year revenue earlier this month.

But what of valuation? With the City currently expecting EPS of about 155 pence, the shares are on a price-to-earnings ratio of about 24, which is way above the long-term FTSE average of around 14.

Thursday, May 23: United Utilities (UU 1.60%)
For our second double date, we'll also have results from United Utilities on May 23, and we're looking at another solid dividend payer. After a cut in 2009, the annual payment has been rising steadily, with a yield of 5.3% achieved last year (based on the share price at the time).

The United Utilities share price has put on about 20% over the past 12 months to reach 743 pence today, bringing this year's expected dividend yield down to 4.7% -- though it should be up in cash terms. City analysts are also expecting earnings growth of about 12%.

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