return filing

as per your question it is implied that your son is is 18 year older since you use the word Major Son.
and you started trading from your major son account and incurred loss under f & o of rupees 10 lakh.

you need to file your own income tax return and your son need to file his own income tax return.

you will file income tax return under the head salary because you are employee.

your son will file income tax return under the head income from business and profession since you are doing trading on behalf of your son and since your son is major son he need to file his own income tax return.

your son can file income tax return under section 44AD. Turnover of your business will be the difference between the sell price and the purchase price.you have to remove all the minus sign from the loss amount and you have to calculate the sum of all incomes and losses.the sum amount will become your turnover and you can show deemed income at 6%. I know you incurred loss of 10 lakh rupees but as per law, when you are dealing in future and option, you need to show your turnover as a difference between sale price and purchase price. so you can show income under 44ad a b and so profit only 6% and you need to pay tax on the 6% of profit only if it is above the threshold limit of 250000.

I suggest you to visit a chartered accountant nearest you to file your income tax return because it's the case of loss under future and option and there are chances for scrutiny of your income tax return.

audit is required when the turnover of an individual is more than 1 Crore. but as per section 44ad income Tax allows for an individual, if turnover is less than 2 crore he can show his deemed income of 8% r 6% as the case may be.

your son is a major son so clubbing of income provisions are not applied on the income of son, so whether your son deals with his own income or your income it will be taxed in hands of your son only.