It may be possible to combine trust funds with the deposit account, if the ownership is the same for all funds, but it may not be advisable. If the only beneficiaries of the trust are the two customers themselves, then they would be considered to be joint owners of the trust funds. See 12 CFR 330.10(f) (stating that a trust account where the only beneficiaries are the account owners would be treated as a joint account). Because the customers own the funds in the original account in joint tenancy, they already have rights of survivorship in the account. Joint Tenancy Act, 765 ILCS 1005/2. If the trust agreement provides for the same rights of survivorship, it may be possible to combine the funds into one account.

Even if that is the case, though, there may be more complications after both customers pass away. If both customers pass away, the trust agreement would govern the trust funds, and probate laws would govern the non-trust funds. Therefore, you may have to segregate trust funds from the joint funds in the end. It may make more sense to just have two separate accounts — one for the trust funds, one for the joint funds.