Can I open a cash ISA this year, before 6th April, and one after the 6th April, I have £11000 so was going to put £5100 in before the deadline and £5340 after, can I top up the first ISA after the 6th April or do I open a new one ?
I don`t really understand the question. If you open an ISA this year you can put 5100 into it. You can`t top it up because as you say, the limit is 5100. If you put 5340 into next year`s you can`t top that up either. You won`t be able to make up this years one to next years limit because you can only have one ISA at a time.
Yes, you are permitted to contribute the maximum in March andthe new maximum at the start of the new tax year. This is provided you haven't already contributed to an ISA in this tax year