When you need to request changes to your visitation schedule, support arrangements, custody or medical support, you will likely need to file an SAPCR.
According to Texas State Law Library, an SAPCR is a Suit Affecting the Parent-Child Relationship.
If there is not a need to establish paternity in your case, then the SAPCR is the way to go to ask for modifications. However, if you have not determined paternity yet, then you will need a paternity case, which will establish paternity and also handle the arrangements for custody, visitation and support details.
You can only file an SAPCR if your child lived in Texas within the last six months. Even if your child no longer lives in the state, you can use an SAPCR if it has been less than six months since the child left the state. It does not matter where the other parent lives as the SAPCR ties to the child, not the parents.
You should note, though, that the court needs jurisdiction over the other parent. The court may have jurisdiction over someone not living in Texas. The form will let you know the specifics and if you can file the SAPCR. You also must serve the other parent to make him or her aware you are filing the SAPCR.
File your documents in the county in which the child lives or last lived when still in the state. If you and the other parent agree on the requests in the document, the court can finalize it within days. Otherwise, you will need to go before the court, which can take longer.