Thanks Charlotte for replying.
Sorry to cause more confusion. I am very new to this so asking it again to be more clear.
My query is all about ISA account not Share dealing account. So can I buy and sell shares on the same day in my ISA account?
e.g. In my ISA account
I add £1000 on Day 1
On Day 5 I buy shares of Company X worth £900
Can I sell those shares on the same day (i.e. Day 5)?