What is the 18.001 Affidavit of Medical Expenses in Texas?

An 18.001 affidavit of medical expenses in Texas is a legal document used in civil actions to establish the amount paid for medical care following an injury. It is outlined in Section 18.001 of the Texas Civil Practice and Remedies Code. The law permits a plaintiff to use a sworn statement from a medical provider or a custodian of records to demonstrate that the medical services were necessary and the charges were reasonable. This affidavit provides the court with proof of medical expenses without requiring live medical expert testimony at trial.

If the other side (the defendant) does not file a counter-affidavit, the affidavit can be used as prima facie evidence that the charges were reasonable and necessary. But the affidavit does not prove that the defendant’s actions caused the injury. It also does not replace the need to show causation in a case.

What is Section 18.001 of the Texas Civil Practice and Remedies Code?

Section 18.001 of the Texas Civil Practice and Remedies Code governs the use of an affidavit regarding the cost and necessity of services in a civil action in Texas courts. This rule only applies to civil actions and not to a lawsuit based on a sworn account.

The primary purpose of Section 18.001 is to help a plaintiff prove that the medical expenses they paid for medical services were reasonable and necessary without hiring an expert witness to testify in person. An affidavit from a medical provider or a custodian of records may serve as evidence of medical charges and related documentation.

Unless the defendant files a controverting affidavit, the affidavit is enough for a judge or jury to decide that the amount charged was reasonable and that the medical services were necessary. The affidavit is not used to prove that the defendant caused the injury. It addresses only the reasonableness and necessity of the charges.

Why does this matter?

In many Texas personal injury claims, proving past medical expenses can cost a lot if you must pay for expert witness testimony. The 18.001 affidavit makes it easier and less expensive for plaintiffs to introduce an itemized statement of their medical care and the charges made into evidence, which can help support their claim for damages.

What an 18.001 Affidavit Must Include and Who Can Make It

An 18.001 affidavit is a special legal document used in Texas personal injury claims to show medical expense documentation in a civil action. To be valid, the affidavit must comply with the requirements of Texas Civil Practice and Remedies Code Section 18.001 so that a judge or jury may use it as evidence that medical services were necessary and that the charges were reasonable.

Required Contents of the Affidavit

To meet the rule, an affidavit must:

Be taken before a person with the power to administer oaths, like a notary public.
Be made by either the person who provided the service or the custodian of records who keeps the medical billing records showing the services and charges.
Include an itemized statement listing each medical service and the amount charged for each.

This means the affidavit must clearly list all medical expense documentation, such as itemized medical billing records, so the court can see what services were given and how much each cost.

Who Can Make the Affidavit

The law says the affidavit must be made by:

A medical provider who actually gave the medical services, or
A custodian of records who is responsible for the official medical billing records showing the services and the charges.

This helps ensure that the person signing the affidavit has direct knowledge of medical services and charges.

Some court decisions have also clarified that other qualified people with knowledge of records and charges may sometimes prepare affidavits. Still, the basic rule is that the person must know the facts in the document.

What the Affidavit Shows

If the affidavit meets all the legal requirements, then, unless the defendant files a controverting affidavit, it is enough evidence for a judge or jury to find that the medical charges were reasonable and the medical services were necessary.

An 18.001 affidavit does not establish causation (i.e., that the defendant caused the injury). It only relates to the reasonableness and necessity of medical expenses.

Filing & Timing Rules

When you use an 18.001 affidavit in a civil action in Texas, you must follow strict filing and timing rules under the Texas Civil Practice and Remedies Code Section 18.001. These rules tell you when the affidavit and any counter-affidavit must be served on the other parties.

When the Plaintiff Must Serve the Affidavit

The plaintiff must serve their 18.001 affidavit on all other parties by the earlier of:

90 days after the date the defendant files an answer,
The date the plaintiff must designate any expert witness under a court order, or
The date by which the plaintiff must designate any expert witness under the Texas Rules of Civil Procedure.

This means the affidavit must be served early in the case, not just before trial. The rule helps ensure that medical expense documentation and itemized medical billing records are provided before expert deadlines.

If the plaintiff gets new medical services after the defendant files its answer, the plaintiff may serve supplemental affidavits for those services on or before the 60th day before the trial starts.

When the Defendant Must Serve a Counter-Affidavit

If the defendant wants to challenge the plaintiff’s affidavit by filing a counter-affidavit, it generally must serve that counter-affidavit within 120 days after the defendant files its answer.

The counter-affidavit must give reasonable notice of why the defendant believes the charges were not reasonable or the medical services were not necessary. The Texas Supreme Court has clarified that the person making the counter-affidavit must be qualified by knowledge, skill, experience, training, or education to speak to the contents.

Why Timing Matters

If either side misses these deadlines, they may lose the chance to rely on an 18.001 affidavit or counter-affidavit as evidence. That can affect how the judge or jury views the medical charges and medical expense documentation at trial.

Some deadlines may be modified if all parties consent or the court permits it, but any such change must be made before the deadlines pass.

Legal Effects of Filing an 18.001 Affidavit

When a plaintiff files an 18.001 affidavit in a Texas personal injury claim, it has specific legal effects under the Texas Civil Practice and Remedies Code Section 18.001. These effects shape how the judge or jury can use the medical expense documentation and affidavit in the civil action.

An Uncontested Affidavit Is Sufficient Evidence

If no controverting affidavit is filed in time, an affidavit stating that the amount charged for medical services was reasonable and that the services were necessary is enough prima facie evidence for the judge or jury to find those facts. That means the affidavit alone can support a finding of fact on whether the medical charges were reasonable and the medical services were necessary.

This makes it easier for a plaintiff to prove past medical expenses in a civil action without the need for a live expert witness. The affidavit, together with medical billing records and itemized statements, constitutes the medical expense documentation supporting the claim.

The Affidavit Does Not Prove Causation

The 18.001 affidavit does not establish whether the defendant caused the injury or condition that gave rise to the medical expenses. It only relates to the reasonableness and necessity of the costs themselves. The Texas Civil Practice and Remedies Code clearly states that the affidavit does not support a finding on the causation element of the injury claim.

This means that even if the affidavit is accepted, the plaintiff must still show that the defendant’s actions caused the injury in other ways in the case.

Effect of a Counter-Affidavit

If the defendant serves a controverting affidavit before the deadline, the legal effect changes. The counter-affidavit challenges the claim that the medical expenses were reasonable or necessary. When a valid counter-affidavit is filed, the affidavit no longer automatically serves as sufficient evidence. The plaintiff may then need to use expert testimony or other evidence at trial to prove that the charges were reasonable and the services were necessary.

A counter-affidavit must clearly explain why the defendant contends that the charges were not reasonable or the services were not necessary. It must be signed by someone qualified by knowledge, experience, training, or education.

Important Court Clarifications

The Texas Supreme Court has clarified the operation of counter-affidavits. A counter-affidavit does not have to meet strict expert witness standards to challenge the reasonableness or necessity of medical fees. Courts focus on whether the person signing the counter-affidavit is qualified and whether the document gives reasonable notice of the challenge.

Even if a court strikes a counter-affidavit for some reason, the defendant is still allowed to present evidence at trial to challenge the reasonableness or necessity of the medical charges.

Counter-Affidavits & Challenges

A counter-affidavit is a key part of the Texas Civil Practice and Remedies Code Section 18.001 when a defendant wants to challenge a plaintiff’s 18.001 affidavit about medical expense documentation in a civil action. If a defendant disputes that the medical charges were reasonable or that the medical services were necessary, the defendant may file a controverting affidavit to explain why.

What a Counter-Affidavit Must Do

A valid counter-affidavit must:

Be served on all other parties within the deadline set by the statute.
Give reasonable notice of the basis on which the defendant will challenge the original affidavit.
Be taken before a person authorized to administer oaths.
Be made by a person qualified by knowledge, skill, experience, training, education, or other expertise to testify against some or all facts in the original affidavit.

The counter-affidavit cannot be used to challenge causation of the injury, only the reasonableness or necessity of the medical charges.

When the Counter-Affidavit Must Be Served

A defendant must generally serve a counter-affidavit on other parties:

No later than 120 days after filing the defendant’s answer,
Or by the party’s expert witness designation deadline under court order or the Texas Rules of Civil Procedure.

If the original 18.001 affidavit was served late under the special rules for new services, then the counter-affidavit deadline is adjusted to either:

30 days after service of that affidavit on the defendant, or
The same expert designation deadlines noted above.

Who Can Sign a Counter-Affidavit

Under the statute, the person signing the counter-affidavit must be qualified by knowledge, skill, experience, training, education, or other expertise to dispute the reasonableness or necessity of the medical charges listed in the original affidavit.

The Texas Supreme Court explained that the person signing a counter-affidavit need not be a doctor in the same medical specialty as the providers named in the original affidavit. The counter-affiant may be someone with broad medical billing, coding, or healthcare experience, provided they can explain why the charges or services are not reasonable or necessary.

The court also held that the counter-affidavit need not comply with the strict rules governing expert testimony under the Texas Rules of Evidence to be valid under Section 18.001.

What Happens When a Counter-Affidavit Is Filed

If a timely and proper counter-affidavit is filed, the 18.001 affidavit is no longer automatically enough to show that all charges were reasonable or necessary. The plaintiff may then be required to present expert witness testimony or other evidence at trial to prove those issues to the judge or jury.

Common Challenges to Counter-Affidavits

Sometimes, plaintiffs try to strike counter-affidavits by claiming the person signing them is not sufficiently qualified or that the opinions are unreliable. The Texas Supreme Court has made clear that:

Courts should not strike a counter-affidavit just because the opinions do not meet typical expert admissibility tests.
A witness need not specialize in the exact medical field involved to be qualified.
The primary focus is whether the counter-affiant is qualified and the affidavit gives reasonable notice of the issues in dispute.

Even if a counter-affidavit is struck, the defendant is not prevented from presenting evidence at trial to dispute the reasonableness or necessity of the medical expenses.

Why This Matters

The counter-affidavit is an essential component of the strategic use of Section 18.001 in Texas personal injury claims. Without a timely counter-affidavit, a plaintiff’s medical expense affidavit may stand as prima facie evidence of reasonableness and necessity. With a valid counter-affidavit, the dispute over medical expenses may become part of the trial, and both parties may need live testimony.

Strategic Use in Texas Personal Injury Cases

In Texas personal injury claims, the 18.001 affidavit is more than a form you file. It is a legal strategy that can shape how the judge or jury sees your medical expense documentation. Lawyers use this tool to save time, reduce litigation costs, and make it easier to establish that medical services were necessary and thatthe amounts charged were reasonable.

How Plaintiffs Benefit

When a plaintiff uses an 18.001 affidavit properly:

It simplifies the admission of medical billing records into evidence. Instead of having a live expert witness testify regarding medical costs, the affidavit helps introduce the expenses at a lower cost and with less delay.
If there is no timely counter-affidavit from the defendant, the affidavit is sufficient evidence to show that the medical care was necessary and that the charges were reasonable.
This lets the plaintiff focus on the core parts of the case, such as causation and liability, without extra expert costs on routine billing issues.

Using the 18.001 affidavit early and correctly can strengthen and clarify the case for the judge or jury regarding past medical expenses.

What Defendants Should Know

For a defendant, the 18.001 affidavit presents both a challenge and an opportunity:

A counter-affidavit lets a defendant challenge the reasonableness or necessity of the medical charges.
Evidence from a counter-affidavit can force the plaintiff to present expert testimony at trial to prove those points if the counter-affidavit is valid.
The Texas Supreme Court clarified that a counter-affidavit can be made by a person who is qualified by knowledge, experience, training, or education to dispute the medical charges, even if they are not in the same medical specialty as the original affiant.

By filing a counter-affidavit, a defendant can compel a plaintiff to prove the details of the medical expenses with live evidence and expert witnesses, which can help the defense at trial.

Planning Ahead

Both plaintiffs and defendants need to think ahead when preparing or responding to an 18.001 affidavit:

Make sure medical records and itemized statements are complete and accurate.
Follow the filing and timing rules under Texas Civil Practice and Remedies Code Section 18.001 to avoid losing the chance to use or challenge an affidavit.
Consider whether live expert testimony might still be needed if a counter-affidavit is served.

Using the 18.001 affidavit well in a Texas personal injury case can help simplify proof of medical costs, limit expensive expert fees, and keep the focus on the real issues in the case.

Practical Tips for Preparing an 18.001 Affidavit

Preparing an 18.001 affidavit for a Texas personal injury claim is easier and more effective when you follow clear steps. The Texas Civil Practice and Remedies Code Section 18.001 lets you use an affidavit to show medical expense documentation without always needing expert witness testimony. However, you must prepare it carefully so that a judge or jury will accept it as evidence that the medical services were necessary and that the amounts charged were reasonable.

Gather Complete Medical Billing Records Early

Start by collecting all medical billing records and itemized statements for every medical service you want to include. Make sure the records show:

The name of the medical provider,
The date of each service,
A clear list of services, and
Each charge is made for those services.

Having complete documentation makes it easier to prepare your 18.001 affidavit and reduces the chance that the defendant can dispute what you are trying to prove.

Choose the Right Person to Sign the Affidavit

The affidavit must be written and signed by a person who knows about the services and charges. In most cases, this will be:

The medical provider who gave the medical services,
Or the custodian of records for the medical billing records.

This helps ensure the affidavit complies with legal requirements and supports a finding of fact that the charges were reasonable and necessary.

Use Clear, Itemized Lists in the Affidavit

Make sure that the affidavit includes:

A clear list of each medical service provided,
The amount charged for each service, and
A statement that the services were necessary and the charges were reasonable.

This detailed list becomes the core of your medical expense documentation in the case and helps the judge or jury understand precisely what you are asking them to accept.

Serve the Affidavit on Time

Under Section 18.001, you must serve your affidavit on the other parties by the deadline set in the statute:

Usually, 90 days after the defendant files an answer,
Or by the expert designation deadline if that comes first.

If you receive new medical bills after that deadline, you can still serve supplemental affidavits before your expert witness designation deadline.

Filing and serving the affidavit on time is crucial. If you miss the deadline, you may lose the chance to use the affidavit as prima facie evidence of reasonableness and necessity.

Work with Legal Counsel

An experienced personal injury attorney can help you:

Organize your medical expense documentation,
Make sure the affidavit meets all the statutory requirements, and
Check that you serve it correctly and on time.

Lawyers know how the Texas Civil Practice and Remedies Code Section 18.001 works in real court cases, and they can reduce the risk of mistakes that could cost you the chance to prove your past medical expenses.

Common Myths & FAQs

This section addresses common questions and dispels myths about the 18.001 affidavit in Texas personal injury claims, using plain English. The goal is to help you understand what the Texas Civil Practice and Remedies Code Section 18.001 affidavit concerning cost and necessity of services does and does not do. The answers here are based on the Texas statute and practical legal guidance.

Myth 1 — The Affidavit Proves the Defendant Caused the Injury

Fact: An 18.001 affidavit shows that the medical services were necessary and that the amount charged was reasonable, but it does not prove causation. This means it cannot legally establish that the defendant caused the accident or injury that gave rise to the medical bills. It applies only to the reasonableness and necessity of the charges.

Myth 2 — You Do Not Need a Lawyer to Prepare an Affidavit

Fact: While you can prepare or help gather medical expense documentation and itemized medical billing records, it is often invaluable to work with a personal injury attorney. A lawyer can help:

Collect complete medical billing records and itemized statements.
Ensure the affidavit complies with legal requirements.
Keep track of deadlines for serving the affidavit or responding with a counter-affidavit.

FAQ — What Happens if the Defendant Files a Counter-Affidavit?

If the defendant files a valid counter-affidavit, the original 18.001 affidavit no longer constitutes automatic proof that the medical charges were reasonable and theservices were necessary. The plaintiff may need to present expert witness testimony or other evidence at trial to prove those issues to the judge or jury.

FAQ — Does the Affidavit Replace All Expert Testimony?

No. An 18.001 affidavit can replace expert testimony only for proving the reasonableness and necessity of medical expenses under Section 18.001. It does not replace expert testimony on other issues in the case, such as causation or other complex medical problems.

FAQ — Can the Defendant Still Challenge the Affidavit at Trial?

Yes. Even if a counter-affidavit is not filed, the defendant may still challenge the reasonableness or necessity of the medical bills at trial using cross-examination or other evidence. However, the rule allows the affidavit to constitute sufficient evidence if unchallenged within the time allowed.

FAQ — What if the Court strikes a Counter-Affidavit?

If a court strikes a counter-affidavit for a procedural reason, the defendant is not necessarily barred from disputing the medical expense charges at trial. The defendant may still introduce other evidence to challenge reasonableness and necessity.

FAQ — Does Section 18.001 Apply in Federal Court?

There is some disagreement among federal courts in Texas about whether Section 18.001 always applies in federal cases under the Erie Doctrine. Some federal courts treat it as procedural, and others use it as part of state law when state law governs the case under federal rules.