Okla. Stat. tit. 43 § 118.3
On or after April 15th of each year, the obligor or obligee may make a written request to the other party for the other party's previous tax year W-2 forms, 1099 form, or other wage and tax information. This request shall be served upon the other party in the same manner prescribed for the service of summons in a civil action, and the original request shall be filed in the court file. The party receiving such a written request shall provide the requesting party a copy of the requested information by certified mail within ten (10) days of receiving the written request. If a motion to modify child support is subsequently filed by the requesting party, and it is shown to the court that the non-moving party failed to comply with this section, the court may award the moving party his or her attorneys fees and costs incurred as a result of the failure to provide requested information.
Okla. Stat. tit. 43, § 118.3