How to Establish Paternity in Washington
Reviewed by DocDraft Legal Team · Washington · Last updated 2026-09-12
In Washington, establishing paternity means legally identifying a child's parent under the Washington Uniform Parentage Act (RCW 26.26A) so the child gains rights to support, inheritance, health coverage, and benefits and the parent gains standing to seek residential time and decision-making. Unmarried parents who agree can establish parentage without court by signing an Acknowledgment of Parentage, provided through the Department of Social and Health Services, Division of Child Support, and filing it with the Department of Health, where it has the same effect as a court order. When parents do not agree, a court adjudicates parentage. The load-bearing Washington rule is timing. There is no statute of limitations to establish parentage: a proceeding to adjudicate parentage may be commenced at any time, even after the child reaches adulthood (RCW 26.26A.400). But a marital presumption is time-limited. A person married to or in a registered domestic partnership with the birth parent at birth is a presumed parent (RCW 26.26A.115), and that presumption generally cannot be overcome after the child attains four years of age (RCW 26.26A.435). Attorney review of your situation is available through DocDraft.
Find out where you stand in Washington
Where are you in establishing paternity?
DocDraft provides document preparation, not legal advice.
How long do I have to establish paternity in Washington?
There is no statute of limitations to establish parentage in Washington. Under RCW 26.26A.400, a proceeding to adjudicate a child's parentage may be commenced at any time, including after the child reaches the age of majority. Time limits apply only to overcoming certain presumptions.
When can the marital presumption be challenged in Washington?
Under RCW 26.26A.435, a presumption of parentage generally cannot be overcome after the child attains four years of age, unless the court determines the presumed parent is not a genetic parent, never resided with the child, and never held the child out as their own, or the child has more than one presumed parent.
What genetic-testing result establishes parentage in Washington?
Under RCW 26.26A.325, testing identifies an individual as a genetic parent when it shows at least a 99 percent probability of parentage, using a prior probability of 0.50, with a combined relationship index of at least 100 to 1. A court orders testing when a party's sworn statement shows a reasonable possibility of parentage.
Can a parentage case be filed after the child is grown in Washington?
Yes. Because Washington sets no statute of limitations to establish parentage, a proceeding to adjudicate a child's parentage may be commenced at any time, including after the child reaches adulthood (RCW 26.26A.400). Only overcoming a presumption is time-limited, and a resulting judgment can support orders for support and residential time.
Washington parentage law at a glance
Washington's Uniform Parentage Act (RCW 26.26A) is unusual for setting no statute of limitations to establish parentage: a proceeding to adjudicate a child's parentage may be commenced at any time, even after the child becomes an adult (RCW 26.26A.400). What is time-limited is overcoming a presumption. A person married to or in a registered domestic partnership with the birth parent at birth is a presumed parent (RCW 26.26A.115), and that presumption generally cannot be overcome after the child attains four years of age (RCW 26.26A.435). Unmarried parents who agree can sign an Acknowledgment of Parentage, filed with the Department of Health, which has the effect of a court order. A court orders genetic testing on a sworn statement showing a reasonable possibility of parentage; testing identifies a genetic parent at a 99 percent probability with a combined relationship index of at least 100 to 1 (RCW 26.26A.325).
Establishing Washington parentage for a child of unmarried parents
Suppose a child is born in Washington to unmarried parents who agree on the second parent. At the hospital both sign an Acknowledgment of Parentage, filed with the Department of Health, giving it the effect of a court order. If one signer later has doubts, they can rescind within 60 days, the federal window; after that a challenge is limited to fraud, duress, or material mistake. Had the parents disputed parentage, either could file in superior court at any time, since there is no statute of limitations to establish parentage (RCW 26.26A.400), and the court could order genetic testing that identifies a genetic parent at a 99 percent probability (RCW 26.26A.325). Had the child been born to a married person, that presumption (RCW 26.26A.115) generally could not be overcome after the child turned four (RCW 26.26A.435). Attorney review is available through DocDraft.
Relevant Laws
RCW 26.26A.400 (commencement of a parentage proceeding)
Provides that a proceeding may be commenced to adjudicate the parentage of a child and, unlike many states, sets no statute of limitations, so such a proceeding may be brought at any time.
RCW 26.26A.115 (presumption of parentage)
Provides that an individual is presumed to be a parent if married to or in a state registered domestic partnership with the woman who gave birth at the time of birth, or if the child is born within 300 days after that marriage or partnership ends.
RCW 26.26A.435 (adjudicating a presumed parent's parentage)
Provides that a presumption of parentage under RCW 26.26A.115 cannot be overcome after the child attains four years of age unless the court determines the presumed parent is not a genetic parent, never resided with the child, and never held the child out as the presumed parent's child, or the child has more than one presumed parent.
RCW 26.26A.325 (genetic-testing identification threshold)
Provides that genetic testing identifies an individual as a genetic parent when the results show at least a 99 percent probability of parentage, using a prior probability of 0.50, and a combined relationship index of at least 100 to 1.
RCW 26.26A.200 (acknowledgment of parentage)
Provides for the voluntary Acknowledgment of Parentage by which the birth parent and a person seeking to establish parentage may establish a parent-child relationship, which once effective has the effect of an adjudication of parentage.
Washington State Division of Child Support
The Department of Social and Health Services, Division of Child Support provides the Acknowledgment of Parentage form, helps parents establish parentage, and establishes and enforces child support once parentage is established.
Regional Variances
Washington parentage rules at a glance
Voluntary path and form
Unmarried parents establish parentage by signing an Acknowledgment of Parentage, provided by the Division of Child Support and filed with the Department of Health, which gives it the effect of a court order.
Rescission window
A signer may rescind within 60 days, the federal window. After that, the acknowledgment can be challenged only for fraud, duress, or a material mistake of fact, within the period Washington law allows.
Deadline to establish
There is no statute of limitations to establish parentage; a proceeding may be commenced at any time, even after the child reaches adulthood (RCW 26.26A.400).
Marital presumption and limit
A person married to or in a registered domestic partnership with the birth parent at birth is a presumed parent (RCW 26.26A.115); that presumption generally cannot be overcome after the child attains four years of age (RCW 26.26A.435).
Genetic-testing threshold
A court orders testing on a sworn statement showing a reasonable possibility of parentage; testing identifies a genetic parent at a 99 percent probability with a combined relationship index of at least 100 to 1 (RCW 26.26A.325).
Who administers it
The Division of Child Support provides the acknowledgment form and helps establish parentage and support; disputed parentage is decided by the superior court, which can order genetic testing.
Suggested Compliance Checklist
Confirm whether a marital presumption applies
Before signing or filing anything days after startingDetermine whether a person was married to or in a registered domestic partnership with the birth parent at the child's birth, or the child was born within 300 days after that relationship ended, which creates a presumed parent (RCW 26.26A.115). That presumption generally cannot be overcome after the child turns four (RCW 26.26A.435).
Get genetic testing if parentage is uncertain
Before signing an acknowledgment days after startingIf there is doubt, a court orders genetic testing on a sworn statement showing a reasonable possibility of parentage. Under RCW 26.26A.325, testing identifies a genetic parent at a 99 percent probability with a combined relationship index of at least 100 to 1.
Sign and file the Acknowledgment of Parentage
At the hospital or a Division of Child Support office days after startingUnmarried parents who agree sign the Acknowledgment of Parentage and file it with the Department of Health, which gives it the effect of a court order. Keep a copy. Attorney review of your parentage matter is available through DocDraft.
Track the 60-day rescission window
Within 60 days of signing days after startingIf you need to cancel a signed acknowledgment, rescind within 60 days of signing, the federal window. After that, a challenge is limited to fraud, duress, or a material mistake of fact, within the period Washington law allows.
File a parentage action if parents disagree
Any time a dispute arises days after startingIf parents do not agree, ask the Division of Child Support for help or file a parentage proceeding in the superior court. Because there is no statute of limitations (RCW 26.26A.400), the action can be brought at any time, and the court can order genetic testing.
Keep records of the acknowledgment, testing, and orders
Ongoing days after startingSave copies of the signed acknowledgment, any genetic-test results, and court papers, and calendar the 60-day rescission window and the four-year limit to overcome a presumption (RCW 26.26A.435) so you do not miss a right-forfeiting date.
| Task | Description | Document | Days after starting |
|---|---|---|---|
| Confirm whether a marital presumption applies | Determine whether a person was married to or in a registered domestic partnership with the birth parent at the child's birth, or the child was born within 300 days after that relationship ended, which creates a presumed parent (RCW 26.26A.115). That presumption generally cannot be overcome after the child turns four (RCW 26.26A.435). | - | Before signing or filing anything |
| Get genetic testing if parentage is uncertain | If there is doubt, a court orders genetic testing on a sworn statement showing a reasonable possibility of parentage. Under RCW 26.26A.325, testing identifies a genetic parent at a 99 percent probability with a combined relationship index of at least 100 to 1. | - | Before signing an acknowledgment |
| Sign and file the Acknowledgment of Parentage | Unmarried parents who agree sign the Acknowledgment of Parentage and file it with the Department of Health, which gives it the effect of a court order. Keep a copy. Attorney review of your parentage matter is available through DocDraft. | - | At the hospital or a Division of Child Support office |
| Track the 60-day rescission window | If you need to cancel a signed acknowledgment, rescind within 60 days of signing, the federal window. After that, a challenge is limited to fraud, duress, or a material mistake of fact, within the period Washington law allows. | - | Within 60 days of signing |
| File a parentage action if parents disagree | If parents do not agree, ask the Division of Child Support for help or file a parentage proceeding in the superior court. Because there is no statute of limitations (RCW 26.26A.400), the action can be brought at any time, and the court can order genetic testing. | - | Any time a dispute arises |
| Keep records of the acknowledgment, testing, and orders | Save copies of the signed acknowledgment, any genetic-test results, and court papers, and calendar the 60-day rescission window and the four-year limit to overcome a presumption (RCW 26.26A.435) so you do not miss a right-forfeiting date. | - | Ongoing |
Frequently Asked Questions
Establishing paternity, which Washington law calls parentage, means legally identifying a child's parent under the Washington Uniform Parentage Act so the child can receive support, inheritance, health coverage, and benefits, and the parent can seek residential time and decision-making. It is done by an Acknowledgment of Parentage or a court proceeding (RCW 26.26A).
Unmarried parents who agree sign an Acknowledgment of Parentage, provided by the Division of Child Support and filed with the Department of Health, which gives it the effect of a court order. If parents disagree, the superior court adjudicates parentage, often after ordering genetic testing (RCW 26.26A.325).
It is a form unmarried parents sign to establish a legal parent-child relationship without going to court. Provided by the Department of Social and Health Services, Division of Child Support, it has the same effect as a court order once signed by both parents and filed with the Department of Health.
No. Under RCW 26.26A.400, there is no statute of limitations to establish parentage, and a proceeding may be commenced at any time, even after the child reaches adulthood. The only hard time limit is the four-year window to overcome a presumption of parentage (RCW 26.26A.435).
Yes, within a limited window. A signer may rescind an Acknowledgment of Parentage within 60 days of signing, the federal rescission window. After that, the acknowledgment can be challenged only for fraud, duress, or a material mistake of fact, within the period Washington law allows.
Under RCW 26.26A.435, a presumption of parentage generally cannot be overcome after the child attains four years of age, unless the court finds the presumed parent is not a genetic parent, never resided with the child, and never held the child out as their own, or the child has more than one presumed parent.
Under RCW 26.26A.325, genetic testing identifies an individual as a genetic parent when the results show at least a 99 percent probability of parentage, using a prior probability of 0.50, with a combined relationship index of at least 100 to 1. A court orders testing on a sworn statement showing a reasonable possibility of parentage.
The Department of Social and Health Services, Division of Child Support provides the Acknowledgment of Parentage form and can help establish parentage and support. Acknowledgments are filed with the Department of Health, and disputed parentage is decided by the superior court, which can order genetic testing.
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