Can one deduct amount invested in a sick company?

Are the shares traded in market? or any purchaser as on date?

No. This is a private company which fell victim to Covid. Bank also declared NPA due to non payment of EMIs for the loan.

Unless you get your shares sold for any meager amount, no loss adjustment possible.

I have a few shares that I am planning to sell to the new owners.

If I sell all my shares can I write off all the amount I invested? If so, can I use this to offset any capital gains from real estate or stocks?

Yes, that is possible.

Thank you. If I sell the shares in this financial year, can I carry forward the loss to future years? I don't anticipate capital gains in this financial year to offset against the losses in the company.

Yes, carry forward of losses to next 8 years is allowed under PGBP & capital gains heads..

Thanks again.

Is it required to file an IT return this year (to take the loss incurred this year) or can I file a return in the year I have capital gains to deduct the loss incurred this year?

I don't file IT return every year as I don't have taxable income in India.

Don't do such mistake. File IT return for the loss claim, before due date.