Many people are unaware that losses they incur from the sale of shares are deductible as a capital loss. This includes investments of shares in companies which have gone defunct and are now worthless. You may claim one half of the loss from the sale of those shares as a deduction against gains that you have earned on sales of other investments, or against any of your income in the year you pass away. If you forgot to report these amounts on your tax return in a prior year, you can still report them in the current year.
You can also re-file a previous year tax return, if it helps to reduce your income tax for that year.