ISA account question

If I have an ISA account, and I know the ISA limit is £20,000. So if I put £20,000 into a fixed ISA account. After a month let say it give me £100. Then my ISA account will be £20,100. Then it will over the £20,000. Is it ok? And then as the next interest will come from the amount more than £20,000, then do I need to pay the tax for the interest from the extra £100? Thanks.

Hi Chun Ho Chan,
The interest generated doesnt count towards the limit. it is only actual funds you deposit that count.
Thank you.