Do You Qualify for a Modification?
Missouri courts will consider modifying child support when there has been a substantial and continuing change in circumstances since the last order was entered. RSMo § 452.370. "Substantial" generally means the new calculated amount would differ from the current order by at least 20% or $100 per month — whichever is greater.
Never stop paying child support while waiting for a modification to be approved. Unpaid child support becomes a judgment against you immediately and cannot be retroactively forgiven — even if the court later reduces your amount. Keep paying the current amount until the court officially modifies the order.
Common Qualifying Changes
✓ Likely Qualifies
Job loss or significant income reduction. Major income increase for either parent. Child's needs significantly changed. Child now lives primarily with paying parent. Other parent's income substantially increased.
✓ Likely Qualifies
Child becomes disabled or has significant new medical needs. Child turns 18 and current order covers multiple children. Health insurance coverage changed significantly. Custody arrangement has changed substantially.
✗ Unlikely to Qualify
Temporary job loss (must be continuing, not temporary). Minor income fluctuations under the 20%/$100 threshold. Voluntary reduction in income to avoid support. Changes that occurred before the last modification.
✗ Will Not Qualify
Simply wanting to pay less without a genuine change in circumstances. The other parent remarrying (their new spouse's income is not counted). Child support feels unfair but circumstances haven't changed.
Missouri uses an "income shares" model. Both parents' gross incomes are combined, and child support is calculated proportionally based on each parent's share of that combined income, the number of children, and other factors including health insurance and childcare costs. This means if the other parent's income increased significantly, you may qualify for a modification even if your income stayed the same. Missouri Form 14 is used for all calculations.
How to File for a Child Support Modification in Missouri
Gather Your Financial Documents
Before you file anything, gather: your last 3 months of pay stubs or proof of income, your last 2 years of tax returns, documentation of the change in circumstances (termination letter, doctor's records, new custody arrangement), the other parent's income information if available, and your current child support order with the case number.
Complete Missouri Form 14
Form 14 is Missouri's Child Support Amount Calculation Worksheet. Every child support case in Missouri requires it. You'll enter both parents' gross monthly incomes, the number of children, health insurance costs, and work-related childcare expenses. The form calculates the presumed correct child support amount. If this number differs from your current order by 20% or $100/month or more — you likely qualify.
✓ Run Form 14 Before You FileCalculate the new amount before filing. If the difference isn't substantial enough to meet the threshold, filing will be a waste of time and money. Your kit includes a step-by-step Form 14 completion guide with examples.
File a Motion to Modify Child Support
File in the same Circuit Court that issued your original child support order — use the same case number. Your Motion must state: the current support amount, the new calculated amount from Form 14, the specific change in circumstances that justifies modification, and the date the change occurred. Attach your completed Form 14.
Serve the Other Parent
The other parent must be formally served with your Motion to Modify. Missouri Rules of Civil Procedure apply — you cannot serve them yourself. Use a process server or the Sheriff. Once served, they have 30 days to file a response.
Attend the Hearing
The court will schedule a hearing after service is completed. Bring all your financial documentation, your completed Form 14, and evidence of the changed circumstances. Both parents present their financial information and the judge calculates the new amount. The modification typically takes effect from the date you filed — not the date of the hearing — so file as soon as you qualify.
⚠ File as Soon as You QualifyMissouri courts generally make modifications effective from the date of filing, not the date the change occurred. If you lost your job three months ago but wait to file, you're still obligated for the full amount for those three months. File as soon as the change happens and you know you qualify.
Get the Modified Order
If the judge approves the modification, a new child support order is issued. Get certified copies from the clerk. If you pay through the Missouri Family Support Payment Center, they will update automatically once the court enters the new order. If you pay directly, both you and the other parent need copies of the new order.
Service of Process in Modification Cases
Service in a modification case follows the same rules as any Missouri civil case. The other parent must be personally served — and you cannot do it yourself.
Get Your Motion Served Right the First Time.
Improper service delays your modification — and every day of delay is a day you're paying the old amount. Civil Process Service (CPS) handles same-day personal service with body cam documentation and a same-day affidavit so your modification stays on schedule.
- Same-day personal service — no waiting for the Sheriff
- Body camera documentation on every serve
- Same-day affidavit of service for your court file
- Skip tracing if the other parent has moved
- Serving St. Louis City, St. Louis County, and surrounding Missouri counties
The Forms You Need
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Motion to Modify Child Support
Your main filing document stating the change in circumstances and requested new amount.
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Form 14 — Child Support Amount Calculation Worksheet
Required in all Missouri child support cases. Calculates the presumed correct support amount based on both parents' incomes.
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Financial Statement / Income and Expense Statement
Detailed breakdown of your monthly income and expenses. Required in most Missouri family law modification cases.
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Order Modifying Child Support
The new court order issued after the hearing. Keep certified copies — update Missouri Family Support Payment Center if applicable.
Missouri Child Support Modification by County
Filing fees, local forms, and procedures vary by county. Your $29.95 kit includes complete details for all 114 Missouri counties plus St. Louis City.
| County | Filing Fee | Local Requirements | Full Details |
|---|---|---|---|
| St. Louis City | ~$65 | Financial statement required | Get Kit |
| St. Louis County | ~$68 | Financial statement required | Get Kit |
| St. Charles County | ~$57 | Financial statement required | Get Kit |
| Jefferson County | ~$54 | Check local rules | Get Kit |
| Jackson County | ~$70 | Financial statement required | Get Kit |
| + 109 More Counties | Varies | Varies | Get Kit |
Everything You Need. One Download. $29.95.
- ✓ Form 14 completion guide with step-by-step examples
- ✓ 20%/$100 threshold calculator
- ✓ Motion to Modify template
- ✓ Financial statement template
- ✓ Document checklist — income proof, tax returns, and more
- ✓ County-specific fees — all 114 Missouri counties
- ✓ Hearing preparation guide
- ✓ Missouri Family Support Payment Center update guide
All 114 Missouri counties included
Free Legal Help in Missouri
Missouri Family Support Payment Center
Where child support payments are processed in Missouri. 1-888-761-6500.
Missouri Division of Child Support Enforcement
State agency that can help with modification in some cases — particularly for public assistance recipients.
Legal Services of Eastern Missouri
Free civil legal help for low-income St. Louis area residents including family law matters.
Missouri Courts Self-Help Center
Official family law forms including Form 14 and modification motions.