You mom's estate and your mom's trust are two seperate entities and may have different beneficiaries. Your bank will not want to be in the middle of any family arguements about who is entitled to the funds and would be on the losing end of a lawsuit in the event that a beneficiary of the estate did not receive funds because they were paid to the beneficiary of trust. As a result, the bank would require a check payable to the estate to be deposited into an account which bears the name of the estate. If these funds are in fact owned by the trust, the maker of the check will need to reissue it.
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I can do all things through Him who gives me strength. (Phillipians 4:13)