I am sorry for your loss.
Form 1310 is not available for E-file or mail as of this writing.
Statement of Person Claiming Refund Due a Deceased Taxpayer should be available on 03/04/21. I would wait to file if possible.
Form 1310 cannot be e-filed. You can prepare the form and then mail it in to the same IRS Service Center as the decedent's tax return would be mailed to. You would complete the form as their personal representative.
See Form and instructions in link below.
https://www.irs.gov/pub/irs-pdf/f1310.pdf
When will my forms be ready?
