Guide · Updated 07/07/2026

Parentage disputes

If the CMS names you as a parent and you believe you are not, act immediately: say so on the first call and follow up in writing. The scheme runs on presumptions, and while a dispute is unresolved you will usually still be expected to pay.

When the CMS presumes you are the parent

Under section 26 of the Child Support Act 1991, the CMS can treat a person as a parent where, among other grounds: they were married to the child's mother at any time between conception and birth; they are named on the birth certificate; they have adopted the child; a court has already found parentage; or they refuse to take a DNA test. If a presumption applies, maintenance is payable unless and until you displace it.

The process

1. Deny parentage at first contact

   Tell the CMS you dispute parentage. If no presumption applies, the case should pause on liability while parentage is resolved. If one applies, the calculation usually proceeds in parallel.

2. DNA testing

   The CMS arranges testing through an accredited provider. The alleged parent pays the fee up front — refunded in full if the test shows you are not the parent. If the test confirms parentage, you remain liable (including for the disputed period). Refusing the test triggers the presumption of parentage: you will be assessed anyway.

3. Court, where needed

   Either side can seek a declaration of parentage (or non-parentage) from the family court under section 55A of the Family Law Act 1986 — the definitive answer where testing is refused, impossible, or the case involves fertility treatment or surrogacy, where genetics do not decide legal parentage.

4. Refunds

   Proved not to be the parent? The CMS should refund maintenance paid — normally from the date you first disputed parentage. This is why disputing immediately, in writing, matters so much: your dispute date anchors the refund.