Include the suite, room, or other unit number after the street address. If the post office does not deliver mail to the street address and the fiduciary has a P.O. box, show the box number instead.
If you want a third party (such as an accountant or an attorney) to receive mail for the estate or trust, enter on the street address line “C/O” followed by the third party's name and street address or P.O. box.
If the estate or trust has had a change of address (including a change to an “in care of” name and address) and did not file Form 8822-B, Change of Address—Business, check the Change in fiduciary's address box in item F.
If the estate or trust has a change of mailing address (including a new "in care of" name and address) after filing its return, file Form 8822-B to notify the IRS of the change.