Mo. Rev. Stat. § 506.366

An offender seeking to bring a civil action or to appeal a judgment in a civil action without the prepayment of fees or security due to indigency shall submit a request to the court to proceed without the prepayment of fees. The request shall include a certified copy of the offender's correctional center account statement, which shall be provided by the department of corrections for the six-month period immediately preceding the filing of the petition or notice of appeal.