The number of Best Buy products has increased significantly in recent weeks as banks and building societies look to attract savers' funds.
And many of this season's variable cash ISAs include large introductory bonuses, designed to boost the initial rate and attract customers.
There are currently 178 variable rate cash ISAs, with 40 of them including an introductory bonus.
The bonuses boost the rate in the first 12 months of the offer, but just the underlying rate – one that is far less generous – is paid from that point.
Figures show that the average rate of interest on offer from variable cash ISAs is 1.91% presently, but for many of the accounts, the majority of the interest is made up by a bonus, which usually only has a shelf-life of 12 months.
The average size of a bonus on variable cash ISAs is 1.32% presently.
"Savers looking for a competitive tax-free investment at the moment are spoilt for choice. We have seen a surge in new ISA products over the past few weeks and this is predicted to continue until the beginning of the new tax year in early April," said Louise Holmes, spokesperson for Moneyfacts.co.uk.
"Out of the current top five variable ISA rates, four include introductory bonuses equating to a substantial portion of the overall rate.
"Savers looking for a competitive rate must bear in mind that no matter how appealing the initial rate looks, the rate of return will drop significantly once the bonus period expires.
"It would be wise for savers opting for these types of accounts to make a note of when their bonus period is due to expire. This should allow enough time to review savings options, transfer funds to another competitive account and ultimately avoid the disappointment of reverting to a measly return."
To begin your search for the best ISA for you, check the Moneyfacts.co.uk ISA Best Buy tables.
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Disclaimer: Information is correct as of the date of publication (shown at the top of this article). Any products featured may be withdrawn by their provider or changed at any time.
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