Mo. Rev. Stat. § 525.230
The garnishee may deduct a one-time sum not to exceed twenty dollars, or the fee previously agreed upon between the garnishee and judgment debtor where and if the garnishee is a financial institution, for his or her trouble and expenses in answering the interrogatories and withholding the funds, to be withheld from any funds garnished, in addition to the moneys withheld to satisfy the court-ordered judgment. Such fee shall not be a credit against the court-ordered judgment and shall be collected first. The garnishee may file a motion with the court for additional costs, including attorney's fees, reasonably incurred in answering the interrogatories in which case the court may make such award as it deems reasonable. The motion shall be filed on or before the date the garnishee makes payment or delivers property subject to garnishment to the court.
§ 525.230, RSMo