The most dangerous dividend mistake is screening for the highest yield and calling it research.

Yield is calculated as: annual dividend ÷ share price. That means yield rises when the share price falls — exactly when a dividend is most likely to be at risk. Investors who screen for yield above 7% are often filtering for companies the market has already decided are in trouble.

A textbook example is Vodafone. For years it carried one of the highest yields in the FTSE 100 — attractive on the surface. But the dividend was funded by debt rather than free cash flow, and in 2019 the company cut it by 40%. Investors who bought for the yield took both the income cut and the price decline.

British American Tobacco presents a similar pattern today: a yield that looks exceptional against the market average, but driven by a share price that has roughly halved over five years as investors price in structural volume decline. The question isn't whether the yield is high — it's whether the cash generation can sustain it.

On openbook, the Cash Flow factor in a company's Risk rating directly addresses this — it measures free cash flow margin and cash return on assets, not just accounting profit. A high yield alongside a weak Cash Flow score is a combination worth taking seriously. Check how the cash flow score looks for Shell vs Vodafone for a concrete comparison.

UK income investors often end up in the same handful of sectors without noticing.

The FTSE 100 dividend story is largely told by five sectors: financials, energy, consumer staples, utilities, and healthcare. These sectors pay most of the index's dividend income — and a UK income portfolio built from FTSE 100 names almost inevitably clusters there.

During 2020, regulators told UK banks including Lloyds and Barclays to suspend dividends as a precautionary measure. Investors with heavy financial-sector income exposure saw a significant portion of their expected income disappear simultaneously — not because of any individual company failure, but because the whole sector was affected at once.

Openbook's sector breakdown on the portfolio tracker shows you exactly where your income is concentrated. It's often more skewed than investors expect.

The mechanics of dividend dates trip up new investors regularly.

You must hold the share before the ex-dividend date to receive the next payment. The share price typically drops by roughly the dividend amount on the ex-date — so buying after the ex-date gets you a marginally cheaper share, but no income from that cycle.

A less obvious mistake: selling after the ex-date but before the payment date. You've already qualified for the dividend (the ex-date is the cutoff), so you'll still receive it even if you no longer hold the shares.

Track upcoming dates for FTSE 100 and FTSE 250 companies via openbook's UK Dividend Calendar or the dedicated FTSE 100 Dividend Calendar.

Dividends don't reduce investment risk — they change the form that return takes.

During the 2020 pandemic, more than 50 FTSE 350 companies cut or suspended dividends within a matter of weeks. Many were considered reliable income stocks: Lloyds, BP, Shell (temporarily), and dozens of smaller companies. The share prices of dividend payers fell just as sharply as growth stocks.

The idea that "at least I'm being paid to wait" is reassuring during calm markets. It becomes less reassuring when the payment stops and the price has also fallen 30%.

On openbook, the Balance Sheet factor in the Risk rating scores financial solvency — interest coverage, net debt to EBITDA, and debt trend. Companies with strong balance sheet scores tend to be better positioned to maintain dividends through downturns. This is worth checking before assuming any dividend is secure.