I love buying dirt cheap dividend shares. But then, who doesn’t? Buying income stocks with low price-to-earnings (P/E) ratios means possible strong share price gains if they eventually re-rate. In the meantime, I can enjoy a flow of market-beating dividends I can use to reinvest to grow my portfolio.

I’m expecting some tasty tax relief to drop into my Self-Invested Personal Pension (SIPP) in October. So I’ve drawn up a list of underpriced passive income gems to consider.

Here are two from the FTSE 100 I’ve just added to my watchlist.

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.

A top REIT

Tritax Big Box (LSE:BBOX) is under extreme pressure as investors rethink future interest rates. With inflation on the up and threatening to explode, central banks globally are tipped to hike rates in the coming months.

This creates real problems for real estate investment trusts (REITs) like this. These debt-laden companies can see their borrowing costs shoot higher. Earnings will also become strained as higher rates push asset values lower.

I see recent share price weakness at Tritax as a potential buying opportunity however. The reason? Its dividend yield’s leapt to 5.7% for this year, and to 6% and 6.5% for 2027 and 2028 respectively.

As an added bonus, the firm’s forward P/E ratio has recently tumbled to 9.1 times. That’s below the 10-year average of 11-12.

Under REIT rules, Tritax must pay at least 90% of annual earnings out in dividends. I expect the firm to remain a brilliant dividend payer as demand for distribution and logistics centres heats up.

An 8.3% income opportunity!

Investec‘s (LSE:INVP) one of the FTSE 100’s top-10 highest yielders for 2026. At 6.6%, its forward reading is seventh on the list.

So what makes it such a dividend hero? Put simply, Investec’s an incredible cash generator with a strong record of shareholder distributions. It’s grown annual dividends for 12 of the last 13 years, as well as making substantial share buybacks.

As the wealth management sector booms, I’m expecting profits and dividends to continue growing long term. A strong Common Equity Tier 1 (CET1) ratio of 13% underpins those solid dividend forecasts in the meantime. Payouts are tipped to keep rising into 2027 and 2028, pushing the dividend yield to 7.2% and 8.3% respectively.

With a P/E ratio of 8.1, Investec also looks seriously cheap relative to predicted earnings. Why? The average P/E for the firm’s sector peers sits at 11-12. Just be mindful that large exposure to South Africa leaves the business vulnerable to more volatility than some of its peers.

For investors hunting underpriced dividend shares it’s worth a close look, though it’s not the only passive income stock I have my eye on…

What income stock do we like better than Tritax Big Box REIT Plc right now?

One of our Share Advisor analysts has just released a brand new stock report that we think is a must-read for any investor looking to try and generate potential income.

And the best bit is that you can see if for yourself, right now, absolutely free of charge!

No jargon. No hard sell. Just a clear look at an income share we think is worth your time.

Royston Wild does not hold any positions in the companies mentioned.