What is the ruling of Islamic law on holding bank ledgers in a real estate company that invests some of its money as fixed-term and fixed-rate deposits, knowing that its only responsibility is to notify when the current account balance exceeds the limit?

The company's depositing of its funds in banks with a fixed interest rate is precisely usury (riba). Your work in monitoring this balance and its increase is an aid to sin, due to the Almighty's saying: "And do not cooperate in sin and aggression," and due to the Prophet's (peace be upon him) saying: "The Messenger of Allah (peace be upon him) cursed the one who consumes usury, the one who feeds it, its scribe, and its two witnesses. He said: 'They are all equal.'" Your work is based on monitoring a usurious account, and anything that leads to the unlawful is considered likewise. Therefore, you must leave this work, for "whoever fears Allah - He will make for him a way out and will provide for him from where he does not expect."