The Financial Conduct Authority has published the regulatory framework for the Lifetime Isa, less than a month before the product is due to be launched.
The FCA provisional rules, published in November, remained largely unchanged in the final guidelines, with just a handful of key modifications, most significantly to risk warnings.
No change was made to the FCA's decision to allow the Lifetime Isa to be sold without advice.
The final rules come almost a year after former chancellor George Osborne announced the Lifetime Isa, or Lisa, in his final budget.
From 6 April, the Lisa will allow people under the age of 40 to begin saving £4,000 a year, plus a 25 per cent government bonus, towards either a first home or their retirement.
The regulator upheld its decision to force providers to issue risk warnings to consumers stating that opting out of a workplace pension in order to set up a Lisa would mean they would forego the employer contribution.
This mandatory risk warning will now be extended to cover consumers with personal pensions that may also receive employer contributions.
Providers will also have to warn customers that Lisa savers may be ineligible to receive some means-tested benefits that pension savers are eligible to receive.
During the consultation period, the FCA stated it received the most industry comment on its plans to force providers to supply Lisa customers with a table of estimated returns at age 60 - the age at which the Lisa may be accessed without tax or penalty.
The FCA rejected criticism of this policy, stating: "The purpose of the generic table is to give investors a general indication of what they might get back from a Lisa at age 60.
"In particular, the table helps to indicate to consumers that holding lower yielding investments such as cash deposits in a Lisa may not lead to appropriate outcomes in terms of retirement savings."
The regulator also rejected suggestions it mandate a similar table for people using the Lisa to purchase a house, saying such a rule would "not be proportionate".
The FCA also declined to change the limit on the value houses eligible to be bought with a Lisa - currently £450,000 - saying this was outside the regulator's scope.
It also upheld its decision to give Lisa customers a 30-day cooling-off period.
While the FCA made very few amendments to the provisional rules, it kept the door open for changes in the future, stating it was "appropriate for the FCA to keep our approach to the Lisa under review as the market for this new Isa develops".
Tom McPhail, head of retirement policy at Hargreaves Lansdown, said the extension of the risk warnings was "a sensible measure" to ensure that people eligible for a workplace pension did not unconsciously give up the employer contribution.
He said they should sufficiently address the political pressures brought to bear on the product, particularly from those who feared it would undermine auto-enrolment.
Former pensions ministers Ros Altmann and Steve Webb have been among the most vocal opponents of the Lifetime Isa, with the latter calling it an "abomination".
This scepticism has extended to much of the industry, and very few providers have committed to offering a Lisa.
Steven Cameron, pensions director at Aegon and a prominent critic of the Lisa, welcomed the risk warnings announced today, but said they were not enough.
"[W]ith the potential for a Lisa to be held for 40 years, we believe the FCA should have gone further in specifying ongoing information and risk warnings, for example to prompt a review of investment strategy if objectives change from house purchase to retirement funding.”
Mr McPhail, meanwhile, confirmed that Hargreaves Lansdown was still on track to launch a Lisa on 6 April.
So far only Hargreaves Lansdown and The Share Centre have publicly confirmed they will have a Lifetime Isa ready for market on 6 April.
james.fernyhough@ft.com
