Surprise, surprise, the Isa has arrived 10 months early. The Individual Savings Account does not come into operation until April 1, 1999, and it is designed to create simple, no-nonsense products that we can all understand.

But that is far too straightforward for the army of product designers who are now moving on to a war footing, writes Simon Bain.

First off the mark is Save & Prosper with its Fast Track Isa. The campaign claims that investors don't have to wait for the Isa to get tax-free savings benefits. All you have to do is invest before June 19 and be paid 7.2% on your savings immediately. ''And come next April, move your money into a Save & Prosper Isa and we'll give you an additional 1.8% p/a fixed rate bonus.''

No, that doesn't mean that if you commit now to taking out an Isa with S & P they will pay you an extra 1.8% a year on the Isa. It means a bonus, equivalent to 1.8% a year from the offer's closing date of June 19.

Nor does it mean that come next April you will be able to switch into a high-interest cash-based Isa. What S & P is offering then is ''a choice of no-load and discounted unit trusts from its range of high-performance funds''.

First, S & P has had its share of low-performance funds too. The choice of fund for an equity-based Isa is a more important task than spotting a high-interest deposit account.

Secondly, the new account is simply a 30-day account that only pays the competitive 7.2% on deposits of #5000 to #7000. The minimum is #3000, and up to #5000 the rate is only 6% and the bonus only 1.5% The minimum value of the cash bonus plus discount on a unit trust for a #5000 investment is said to be #332.

The bottom line is that this the first of dozens of smart ideas aimed at making you somebody's Isa customer. Watch and wait.

RATING *

*** Worth considering

** Shop around

* Hype alert