When an individual dies, a new entity, distinct from the deceased, called an estate, comes into existence.

You need to look closely at the trust document to see what the grantor intended for the trust after their death. Did they want the trust to terminate upon death? Did they want the trust to continue as a separate taxable trust?

An estate can use a fiscal or calendar year for tax reporting, while a trust must adopt a calendar year. That means, an irrevocable trust that came into existence in 2020 had April 15, 2021 to file an income tax return or an extension.

An EIN is required for both estates and trusts meeting certain conditions. So, you want to look at who the EIN belongs to.