I have an isa account with trading212. I have invested 15k and when the returns including the investment is 20K, I have withdrawn 10K. The maximum allowance in a calendar year is 20K. But I want to know how much more can I invest now within the remaining calendar year.
It is a mistake to withdraw money from an ISA unless it is really needed for something and no other source of funds can be found. The tax savings advantages on that deposit are lost forever. The fact that you are now thinking of additional deposit means that perhaps that withdrawal of 10k was not necessary.
Yes, £20k is annual deposit allowance, in your case the maximum you can deposit is £5k this year.
However you portfolio is not restricted to £20k balance in a calendar year it can shoot up to X amount in an year or over over the time period.
Ex. (Deposit £20k in ISA)
Made a profit of £10k, and you closed your position. Your balance is £30k you are allowed to reinvest this £30k without any restrictions.