Not an expert but can give some advice
This last date is for financial year ended on March 2021, not for current financial year. SO whatever you do now, will not have any relation with that last date.
I am not sure i understand your query correctly, but bringing in capital of 80K in your trading account is no way relevant to Income Tax.
You pay tax on your profits not on capital you used. So if you have 80K you can start trading with it as soon as you like. You need to pay tax on profits which you make from it (not on capital you used)