By "estate taxes" do you mean real estate taxes sometimes called property taxes? Property taxes are generally paid to your local tax collector rather than being filed with the IRS. I only ask because generally estate taxes are not paid annually. They are paid only when someone passes away.
If you do mean property (or real estate) taxes then you can include them as a deduction on your personal income tax return. Whether you file them on your late husband's return will depend on when he passed away and when the taxes are paid. If they are paid after he passed, then the more appropriate place to file them is on your personal return. You may not see a full deduction for these taxes though, since under the new tax law deductions for state taxes is limited.
