While many of us are looking forward to our ISA allowances increasing to £20,000 per year in April 2017, we mustn’t forget that we have an allowance of £15,240 coming our way this April, and very likely some of the current year’s allowance left to use up. So where should we stash our ISA cash?

My view is that it should be mostly in safe and reliable blue-chip shares, and they don’t come much safer or more reliable than Unilever (LSE: ULVR). It owns a whole host of worldwide household brands, including Dove, Hellmann’s, Surf, Sunsilk, Ben & Jerry’s, Colman’s, Lipton… and who could forget Pfanni and Sariwangi? It’s almost impossible to run a modern household without using some of Unilever’s products.

Unilever isn’t a super high-flying growth stock, but since the start of 1990 the value of its shares has still multiplied sixfold to reach 3,091p, while the FTSE 100 has managed just 150%. And Unilever’s growth has been far safer than any blue-sky growth candidate. Unilever also doesn’t pay the highest dividends in the word, but its average annual yield of a little over 3% is around the FTSE average and is well covered by earnings.

So, dividend yields that beat cash savings, plus that very nice long-term share price growth —  I’d say that makes Unilever a very safe cornerstone for a multi-decade ISA.

Technology too?

Moving towards a bit more risk now, I think BT Group (LSE: BT.A) is a candidate worth considering too. BT was hammered by the technology boom and bust at the turn of the century, so it hasn’t matched Unilever in the super-long stakes. But over the past five years BT shares have gained 155% to 445p (against just 8% for the FTSE). And now that the world has a more rational approach to technology, I can’t see anything like the dotcom madness hitting BT again.

BT’s dividends should be a bit above average with forecasts suggesting 3.8% by March 2018, and they’re well enough covered. Since BT completed its acquisition of EE, the UK’s largest mobile network, it’s able to offer the full range of telecoms services — fixed and mobile phones, broadband internet, and television content.

BT’s inroads into the lucrative TV sports market suggest to me that it has a strong future, and with its shares being on a modest P/E of 14.7 for the year ending March 2016, dropping to under 13 based on forecasts for 2018, I see BT as a good long-term ISA bargain.

Cash from gas

My final choice is an out-and-out dividend stock in the shape of Centrica (LSE: CNA), the owner of the British Gas and Scottish Gas brands. Centrica has been paying dividend yields of around 5% and better for years, and we have 5.3% forecast for this year followed by 5.5% in 2017. With the forward visibility of the industry, both in terms of supplies and costs and of customer demand, not much cover is needed and so Centrica can pay out most of its earnings as dividend cash.

The share price has been erratic of late and has actually fallen by 43% since a peak in September 2013, to 227p, as Centrica will have suffered three years of falling earnings should this year’s forecasts prove accurate. But that should level off in 2017, and I can see this year turning out to be a good time to buy Centrica for the long term.

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