In any single tax year, you can take out:
ONE maxi-ISA
or
Up to TWO mini-ISAs
and
ONE Tessa-only ISA
You cannot combine a maxi-ISA and a mini-ISA or two mini ISAs of the same component type in the same tax year. If you did this in the past, the Inland Revenue would wind up the 'illegal' ISA and then apply the appropriate tax and then deduct this from the proceeds.
However, the Inland Revenue changed the rules in January 2003 so that people who mistakenly open a second ISA may be allowed to keep it. The Inland Revenue will decide whether the erroneous ISA is eligible for repair and, if so, will instruct the ISA manager how to proceed. All tax allowances up to the date that the invalid ISA was discovered will be lost. Finally, the total amount invested must not exceed the current annual limit.
This doesn't stop you taking out a maxi-ISA in one tax year, but then taking out two mini-ISAs in the following tax year.
Note that whereas the components in a maxi-ISA all have to be managed by the same ISA-manager, you can take out mini-ISAs with two different managers which gives you a bit more flexibility.
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