Beware the brand new Isa bonus trick (spoiler – it solely lasts 3 months then your fee plummets), warns SYLVIA MORRIS

It’s the final ten-day countdown to use your cash Isa allowance and I urge you to act now before it’s too late.

However, I must warn you of a new trick savings providers are using that could easily trip you up if you’re in a hurry.

You have an allowance of up to £20,000 to use by the end of the tax year on April 5. I recommend that you use of it what you can – and from April 6 consider using next year’s allowance, too.

This precious allowance is under threat and could be reduced to £4,000 by April next year.

This will make it even more likely that you could face a tax bill on savings, making cash Isas even more valuable, as all interest you earn here is tax free.

There are plenty of new accounts with rate increases popping up daily.

Rate drop: Many of the new Isa accounts popping up come with a bonus which only lasts three months

But you must beware. Many of these accounts now come with a bonus – which lasts only three months.

Trading 212 and Moneybox upped their rates to 5.28 per cent on Monday, while Chip pays 5.26 per cent – but if you want a top rate you will likely have to switch again once their bonuses end after just three months.

We are used to providers offering a bonus on their underlying rate which lasts for a year. But this moves it to a whole new level. 

If you want an account run by an app, you will do better with Tembo as things stand. It pays 4.8 per cent with no bonus.

Chip’s rate drops to 4.32 per cent after three months, giving you an annual rate of 4.55 per cent; Trading 212 goes down to 4.5 per cent, giving you just under 4.7 per cent for the full year; while with Moneybox you earn 4.47 per cent as the rate drops to 4.2 per cent after three months. 

These are not bad rates (for now, and only available to new customers). But while the 5.28 per cent rate looks enticing, after three months they are really only on a par with the likes of the 4.56 per cent from Kent Reliance, which has no bonus.

Zopa Bank also cut its bonus time from 12 to three months while upping its rate from 4.3 per cent to 5.01 per cent last week. After three months your rate drops to a much lower 3.8 per cent.

Such is the competition among Isa providers that you can seemingly earn more now than a year ago – when the Bank of England base rate stood at 5.25 per cent.

Despite the 0.75 percentage point fall to 4.5 per cent now, easy-access Isas are now offering as much as 5.28 per cent, up from 5.15 per cent a year ago.

The main battle for our easy-access money comes from new app-based accounts, which you operate from your smartphone.

Some of these have changed their rates five times in the past three weeks as they battle it out to sit at the top of the best buy tables.