Treasury proposals recommend funds should be put by default into a taxed savings account chosen by the provider.
In response to the Government consultation, Tisa says cash Isas are the best outcome to boost consumer savings.
It says cash rolled over from the Saving Gateway should not count towards the annual Isa subscription limit but should be treated by the receiving provider as an Isa transfer.
Director-general Tony Vine-Lott says: “We feel that the key to the success of the scheme will be its simplicity and, wherever possible, its similarities with other successful Government-incentivised schemes like the child trust fund and Isa.
“We believe that defaulting into an Isa on maturity will make the scheme clear, simple and easy to understand from the point of view of the saver while at the same time being the most cost-efficient process for the provider.”