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Texas Civil Practice and Remedies Code §18.001: affidavits on the cost and necessity of medical and other services

The official text of the Texas statute on affidavits that a charge for a service was reasonable and the service was necessary, often used for medical bills in injury lawsuits, with the service deadlines, the counteraffidavit rules and the statutory forms, explained in plain language. Text last checked October 29, 2026.

8 min readPublished October 29, 2026Last updated October 29, 2026Edited by Joseph Budzinski, CTO, InjuryClaimGuide

The short answer

Texas Civil Practice and Remedies Code §18.001 lets a party in a civil lawsuit use a sworn affidavit "that the amount a person charged for a service was reasonable at the time and place that the service was provided and that the service was necessary." Unless a counteraffidavit is served as the section provides, the affidavit "is sufficient evidence to support a finding of fact by judge or jury that the amount charged was reasonable or that the service was necessary" (CPRC §18.001(b)). It is often used for medical bills in injury lawsuits, but the section covers any service. It is not evidence of causation.

This entry provides general informational guidance and is not legal advice.

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Key facts (as of October 29, 2026)

  • Civil actions only. The section applies to civil actions, but not to an action on a sworn account (§18.001(a)).
  • Reasonable and necessary. An uncontroverted affidavit is sufficient evidence to support a finding that the amount charged was reasonable or that the service was necessary (§18.001(b)).
  • Not causation. The affidavit "is not evidence of and does not support a finding of the causation element" of the cause of action (§18.001(b)).
  • Deadlines tied to the case. Service deadlines run from events in the lawsuit, such as the defendant's answer and expert designation dates (§18.001(d)-(e)).
  • Statutory forms. Section 18.002 sets out forms, including one for an affidavit concerning proof of medical expenses (§18.002(b-1)).
  • Last amended in 2019. The history line for §18.001 lists Acts 2019, 86th Leg., ch. 779 (H.B. 1693) as its most recent amendment.

What does §18.001 say?

The official text of Tex. Civ. Prac. & Rem. Code §18.001(a) through (c), as published by the Texas Legislature:

Sec. 18.001. AFFIDAVIT CONCERNING COST AND NECESSITY OF SERVICES. (a) This section applies to civil actions only, but not to an action on a sworn account.

(b) Unless a controverting affidavit is served as provided by this section, an affidavit that the amount a person charged for a service was reasonable at the time and place that the service was provided and that the service was necessary is sufficient evidence to support a finding of fact by judge or jury that the amount charged was reasonable or that the service was necessary. The affidavit is not evidence of and does not support a finding of the causation element of the cause of action that is the basis for the civil action.

(c) The affidavit must: (1) be taken before an officer with authority to administer oaths; (2) be made by: (A) the person who provided the service; or (B) the person in charge of records showing the service provided and charge made; and (3) include an itemized statement of the service and charge.

Source: Tex. Civ. Prac. & Rem. Code §18.001, statutes.capitol.texas.gov. Text last checked October 29, 2026.

What does it mean in plain language?

  • It is a way to prove two things. The affidavit addresses whether a charge was reasonable and whether a service was necessary. It is a sworn statement, signed before an officer who can administer oaths, by the provider or by the person in charge of the provider's records.
  • It needs an itemized statement. The affidavit must include an itemized statement of the service and the charge.
  • It works unless it is challenged in time. If no counteraffidavit is served as the section provides, the affidavit is enough evidence to support a finding by the judge or jury on those two points. The section does not say the judge or jury must make that finding.
  • It does not prove causation. Whether an injury caused the need for the service is a separate element of the case. The section says the affidavit is not evidence of it.
  • It is about lawsuits. Section 18.001 applies to civil actions. It does not itself set any rule for an insurance claim.

What are the deadlines and the counteraffidavit rules?

  • Serving the affidavit. The official text of §18.001(d):

(d) The party offering the affidavit in evidence or the party's attorney must serve a copy of the affidavit on each other party to the case by the earlier of: (1) 90 days after the date the defendant files an answer; (2) the date the offering party must designate any expert witness under a court order; or (3) the date the offering party must designate any expert witness as required by the Texas Rules of Civil Procedure.

  • A new provider after the answer. If services are provided for the first time by a provider after the defendant files an answer, the affidavit for that provider must be served by the earlier of the two expert designation dates (§18.001(d-1)).
  • Notice to the clerk. The offering party or the attorney must file notice with the clerk of the court when serving the affidavit; except as provided by the Texas Rules of Evidence, the affidavit itself is not required to be filed with the clerk before the trial commences (§18.001(d-2)).
  • Serving a counteraffidavit. A party intending to controvert a claim reflected by the affidavit must serve a counteraffidavit by the earlier of 120 days after the date the defendant files its answer or the applicable expert designation date (§18.001(e)). If the affidavit was served under subsection (d-1), the counteraffidavit deadline is the later of 30 days after service of the affidavit or the applicable expert designation date (§18.001(e-1)).
  • What a counteraffidavit must contain. The official text of §18.001(f):

(f) The counteraffidavit must give reasonable notice of the basis on which the party serving it intends at trial to controvert the claim reflected by the initial affidavit and must be taken before a person authorized to administer oaths. The counteraffidavit must be made by a person who is qualified, by knowledge, skill, experience, training, education, or other expertise, to testify in contravention of all or part of any of the matters contained in the initial affidavit. The counteraffidavit may not be used to controvert the causation element of the cause of action that is the basis for the civil action.

  • Continuing services. If continuing services are provided after a relevant deadline, a party may supplement its affidavit on or before the 60th day before the date the trial commences, and a party that served a counteraffidavit may supplement it on or before the 30th day before that date (§18.001(h)).
  • Changing a deadline. A deadline under the section may be altered by all parties to an action by agreement or with leave of the court (§18.001(i)).

These deadlines count from events inside a lawsuit. They are separate from the general two-year period to bring suit for personal injury (§16.003).

What other rules sit next to it?

  • The forms. Section 18.002 sets out a form for an affidavit by the person who provided the service, a form for one by the person in charge of records, and, in subsection (b-1), a form for an affidavit concerning proof of medical expenses by a custodian of records, which is sufficient if it "substantially complies" with the form. The (b-1) form states the total amount paid for the services and the amount currently unpaid that the provider has a right to be paid after any adjustments or credits. Under §18.002(b-2), if a bill attached to that affidavit reflects a charge that is not recoverable, the reference to that charge is not admissible, and under §18.002(c) the forms are not exclusive (§18.002).
  • Paid or incurred. Separately, "recovery of medical or health care expenses incurred is limited to the amount actually paid or incurred by or on behalf of the claimant" (§41.0105). The §41.0105 entry quotes it and how the Supreme Court of Texas read it.
  • Expressions of sympathy. Chapter 18 also says a court in a civil action may not admit a communication that expresses sympathy or a general sense of benevolence relating to the pain, suffering, or death of an individual involved in an accident, made to that individual or a person related to the individual within the second degree by consanguinity or affinity, when it is offered to prove liability of the communicator. A communication that also includes a statement concerning negligence or culpable conduct is admissible to prove liability (§18.061).

What applies in Houston and Harris County?

Section 18.001 applies in civil actions in Texas courts statewide, including the courts in Harris County; no separate Harris County rule on these affidavits was found. The notices in subsections (d-2) and (g) go to the clerk of the court where the case is pending. For a case in a Harris County district court, the guide on looking up a case with the Harris County District Clerk explains how that office's online records can be searched.

When was this checked, and can it change?

The text above was last checked on October 29, 2026, against the official text published by the Texas Legislature. The Legislature can amend a statute in any session. It convenes in regular session on the second Tuesday in January of each odd-numbered year (Gov't Code §301.001), so the next regular session begins on January 12, 2027. This entry is scheduled to be rechecked against the official text by April 2027 and again after the 2027 regular session ends.

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Frequently asked questions

What is an 18.001 affidavit in Texas?
It is an affidavit under Tex. Civ. Prac. & Rem. Code §18.001 that the amount a person charged for a service was reasonable at the time and place that the service was provided and that the service was necessary. Unless a controverting affidavit is served as the section provides, it is sufficient evidence to support a finding of fact by judge or jury that the amount charged was reasonable or that the service was necessary.
Does an 18.001 affidavit prove that the injury caused the medical bills?
No. §18.001(b) says the affidavit is not evidence of and does not support a finding of the causation element of the cause of action that is the basis for the civil action. §18.001(f) says a counteraffidavit may not be used to controvert the causation element either.
Who can sign an 18.001 affidavit?
Under §18.001(c), the affidavit must be taken before an officer with authority to administer oaths, must be made by the person who provided the service or the person in charge of records showing the service provided and charge made, and must include an itemized statement of the service and charge.
When must an 18.001 affidavit be served?
Under §18.001(d), the party offering it, or the party's attorney, must serve a copy on each other party by whichever of these comes first: 90 days after the date the defendant files an answer, the date the offering party must designate any expert witness under a court order, or the date the offering party must designate any expert witness as required by the Texas Rules of Civil Procedure. Subsection (d-1) sets a different rule for a provider who first provides services after the answer is filed, and subsection (i) lets the parties change a deadline by agreement or with leave of the court.
What is a counteraffidavit under 18.001?
A party intending to controvert a claim reflected by the affidavit serves a counteraffidavit under §18.001(e) and (f). It must give reasonable notice of the basis on which the party intends at trial to controvert the claim, must be taken before a person authorized to administer oaths, and must be made by a person qualified by knowledge, skill, experience, training, education, or other expertise to testify in contravention of all or part of the initial affidavit.
Is there a standard form for a Texas medical expense affidavit?
Yes. §18.002 sets out forms for an affidavit by the person who provided the service and by the person in charge of records, and §18.002(b-1) sets out a form for an affidavit concerning proof of medical expenses, by a custodian of records, that is sufficient if it substantially complies. §18.002(c) says the forms are not exclusive.
Does InjuryClaimGuide say whether a medical charge is reasonable?
No. InjuryClaimGuide is a legal advertising service. It does not review bills, evaluate any claim or apply the law to anyone's situation. An attorney can advise you about your specific situation.

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