Trust - which state to file?

[AnnL]

I have a client whose parents had grantor trusts. 

They have passed away, so the trusts are now irrevocable.  The trusts were set up in AZ and the grantors died in AZ.

In previous years, the client, who is now the only fiduciary and beneficiary, lived in AZ, so the trusts were filed in AZ.

For 2025, the client is a full-year resident of IL.

According to AZ law, a trust's state is based on the location of the fiduciary. So, since there are no AZ fiduciaries, this would no longer be an AZ trust.

However, under IL law, a trust's state is based on the location where the grantor died, so this would not be an IL trust.

Where do I file the trust returns, and, therefore, which state's income is this when it flows to the beneficiary's return?

[BobKamman]

Since the beneficiary is an Illinois resident, he pays Illinois tax on the distributions.  I think a trust with a resident trustee and beneficiary is a resident trust for Illinois purposes, but it doesn't really matter if you call it a nonresident.  The beneficiary gets taxed either way.  

[AnnL]

I completely agree that the income (which is all from investments) will flow to the IL individual return. 

But, I am preparing the trust return right now. In previous years, an AZ trust return was filed. What state should the TRUST be filing?