Per IRS Instructions for Form 1040, page 93:

Death of a Taxpayer

If a taxpayer died before filing a return for 2017, the taxpayer's spouse or personal representative may have to file and sign a return for that taxpayer. A personal representative can be an executor, administrator, or anyone who is in charge of the deceased taxpayer's property. If the deceased taxpayer didn't have to file a return but had tax withheld, a return must be filed to get a refund. The person who files the return must enter "Deceased," the deceased taxpayer's name, and the date of death across the top of the return. If this information isn't provided, it may delay the processing of the return.

If your spouse died in 2017 and you didn't remarry in 2017, or if your spouse died in 2018 before filing a return for 2017, you can file a joint return. A joint return should show your spouse's 2017 income before death and your income for all of 2017. Enter "Filing as surviving spouse" in the area where you sign the return. If someone else is the personal representative, he or she must also sign.

The surviving spouse or personal representative should promptly notify all payers of income, including financial institutions, of the taxpayer's death. This will ensure the proper reporting of income earned by the taxpayer's estate or heirs. A deceased taxpayer's social security number shouldn't be used for tax years after the year of death, except for estate tax return purposes.

Claiming a Refund for a Deceased Taxpayer

If you are filing a joint return as a surviving spouse, you only need to file the tax return to claim the refund. If you are a court-appointed representative, file the return and include a copy of the certificate that shows your appointment. All other filers requesting the deceased taxpayer's refund must file the return and attach Form 1310.

To enter the death of a taxpayer or spouse in TaxAct:

1. From within your TaxAct return (Online or Desktop) click on the Federal tab. On smaller devices, click in the upper left-hand corner, then choose Federal. 
2. Click Basic Information to expand the category, then click Taxpayer or Spouse Deceased
3. After you enter the date of death for the appropriate spouse, TaxAct will print "Deceased", the name of the decedent, and the date of death at the top of Form 1040