With the deadline for using this year’s £20,000 Isa allowance just over a month away on April 5, it’s time to pay them a bit more attention. It is still possible to get interest of more than five percent, free of income tax for life.

But first, it is important to dispel a couple of longstanding myths about cash Isas.

The first is that standard non-Isa savings accounts always pay a higher rate of interest. That is not automatically the case today, said Sarah Coles, head of personal finance at savings platform Hargreaves Lansdown.

“Many providers are pulling out the stops to attract new customers before the annual deadline, especially easy access and one-year fixed rates."

For years, savers have not had to worry about paying tax on their interest, thanks to the personal savings allowance.

The PSA allows basic rate taxpayers to earn £1,000 of interest free of tax each year, while higher rate 40 percent taxpayers can take £500.

Today's higher savings rates mean around 2.7million savers now breach their PSA and pay tax. "This puts cash ISAs firmly in the frame,” Coles said.

As ever, savers should shop around rather than taking whatever their bank offers. The best rates are almost always online.

The Moneybox Cash Isa is today's market leader paying more than 5.09 percent with easy access on a minimum opening balance of £500.

But there’s a catch.

This best buy rate is only available via mobile app but is inflated by a 0.94 percent bonus that is paid for just 12 months.

After that, the headline interest rate will fall sharply.

Virgin Money's Defined Access Cash E-Isa is in second place, according to Moneyfacts, paying 5.06 percent with no bonus.

However, it has a catch too, as savers are restricted to just three withdrawals a year. On the fourth, the interest rate will fall to just two percent.

Charter Savings Bank's Easy Access Cash Saver pays 5.03 percent. This online account does not include a time-limited bonus or a limit on withdrawals. However, there's also a catch as the minimum balance is higher at £5,000.

Harpenden Building Society's Cash Isa Account is simpler. It pays 5.01 percent with no bonus or withdrawal limits. Minimum deposit is just £1. This account is only available via the society's website.

Kent Reliance Building Society's Easy Access Cash Isa also pays 5.01 percent on £1,000 and above. Smaller sums earn just 0.1 percent. This is available online or via one of its nine branches, all restricted to the south of England.

Family Building Society's Market Tracker Cash Isa pays five percent on £500 or more, online only.

All of these are notably higher than the inflation rate which stood at four percent in January and may fall as low as two percent by April. For once, savers are getting an inflation-busting return.

Anna Bowes, founder of rate-tracking service Savings Champion, said the problem with easy access rates is that they are variable and will start falling when the Bank of England starts cutting interest rates.

The first cut could come as early as May or June, she said. “If you can lock your money away for a while, consider a fixed-rate cash Isa.”

READ MORE: Six best ISAs for savers and investors explained - including key 'loophole'

Two-year cash Isa fixed rates are notably lower, though, with Shawbrook paying 4.69 percent on a minimum opening balance of £1,000. United Trust Bank pays 4.65 percent on £5,000 or more.

For those who can tie up their money for longer, United Trust Bank pays 4.05 percent for five years on £5,000 and above. Paragon Bank pays 3.75 percent on a minimum £500. This can be opened by post as well as web.

Just a few months ago, five-year fixed rate cash Isas paid more than five percent, but those days are now gone as banks anticipate that first rate cut.

Those who still want branch or telephone access may have to accept a lower rate.

The Halifax Isa Saver Fixed can be opened in a branch or by phone, but pays just 3.20 percent over five years. Like it or not, going online pays.