The $400 tolerance: estimate discipline that avoids disputes

How accurate does a good-faith estimate have to be?

It has to be made in good faith, not made perfect. A good-faith estimate is an honest projection of the charges you reasonably expect for the service, built from your standard rates and the information you have when you issue it 1Ref 1Office of the Federal Register (2026).45 CFR Part 149 — Surprise Billing and Transparency Requirements.The operative rule text for good-faith-estimate content and the patient-provider dispute process, including the substantial-difference ($400) threshold that opens a dispute and the estimate's status as a projection rather than a binding quote.2Ref 2Centers for Medicare & Medicaid Services (2026).No Surprise Billing.That the No Surprises Act requires good-faith estimates for self-pay and uninsured patients and creates the patient-provider dispute-resolution process available when a bill exceeds the estimate, with CMS hosting the implementing guidance.. There is no requirement that the final bill match the estimate to the dollar. What the rule cares about is that the number was a sincere projection rather than a placeholder or a lowball.

The reason accuracy matters in practice is the dispute threshold, not a demand for precision. Once a final bill runs far enough past the estimate, a self-pay patient gains a formal way to challenge it. So the working standard for a solo practice is straightforward: estimate honestly from your real fees, and the gap that would open a dispute rarely appears. Discipline, not clairvoyance, is what the rule rewards.

The $400 tolerance, precisely

The number that matters is the substantial-difference threshold. A self-pay or uninsured patient may take a bill to the patient-provider dispute process when the amount billed exceeds the good-faith estimate by at least $400 for a given provider 1Ref 1Office of the Federal Register (2026).45 CFR Part 149 — Surprise Billing and Transparency Requirements.The operative rule text for good-faith-estimate content and the patient-provider dispute process, including the substantial-difference ($400) threshold that opens a dispute and the estimate's status as a projection rather than a binding quote.2Ref 2Centers for Medicare & Medicaid Services (2026).No Surprise Billing.That the No Surprises Act requires good-faith estimates for self-pay and uninsured patients and creates the patient-provider dispute-resolution process available when a bill exceeds the estimate, with CMS hosting the implementing guidance.. Below that gap, there is no dispute basis on the difference; at or above it, the patient has a formal path to contest the overage before a dispute-resolution entity.

This is what people mean by the $400 rule, and it is the practical tolerance to aim under, not a license to miss by $399 on purpose. The dispute process can limit what you are entitled to collect toward the estimate you gave, so a large overage is not just a paperwork event — it can cost you the difference. The window is generous enough that an honest estimate almost never breaches it.

What "good faith" actually means

Good faith is a standard about your process, not a guarantee about the outcome. The estimate must reflect the items and services you reasonably expect to furnish, priced at the rates you actually charge, using the information available at the time you prepare it 2Ref 2Centers for Medicare & Medicaid Services (2026).No Surprise Billing.That the No Surprises Act requires good-faith estimates for self-pay and uninsured patients and creates the patient-provider dispute-resolution process available when a bill exceeds the estimate, with CMS hosting the implementing guidance.. You are not expected to foresee a course of care that changes for clinical reasons you could not have known. You are expected not to understate what you already know is likely.

That distinction protects you. If a patient's care genuinely expands after you issued a sincere estimate, the estimate was still made in good faith. What fails the standard is a number you knew was low when you wrote it — a figure chosen to win the patient rather than to inform them. Pricing from your standard fee schedule, every time, is the simplest way to keep the estimate honest on its face.

Building an estimate that stays inside the window

An estimate that lands close to the bill is built, not guessed. The discipline is a short, repeatable set of moves you can run at the front desk in a couple of minutes, and it is the same whether you are writing a one-visit estimate or the recurring-care GFE that covers a course of therapy across the year.

• Itemize by code — list each expected service with its diagnosis and service code and expected charge, not a lump sum
• Price from your real fee schedule — the number a patient sees should be the number your billing system would produce
• Include reasonably expected add-ons — if a visit usually brings a companion service, estimate it too
• State your assumptions — note what the estimate is built on, such as an expected number of sessions
• Reissue on a material change — when the plan or scope shifts, a fresh estimate resets the window

The same template that makes a clean estimate at the gfe at the front desk also produces the record you would show if a bill were ever questioned. Whether it is gfes for a weekly service or a single visit, the itemized, fee-schedule-based estimate is the one that stays inside the tolerance.

When the bill will legitimately differ

Bills and estimates diverge for honest reasons, and the rule leaves room for that. Care can extend, a plan can change, an unexpected service can become necessary — none of which makes the original estimate a bad-faith number 1Ref 1Office of the Federal Register (2026).45 CFR Part 149 — Surprise Billing and Transparency Requirements.The operative rule text for good-faith-estimate content and the patient-provider dispute process, including the substantial-difference ($400) threshold that opens a dispute and the estimate's status as a projection rather than a binding quote.. The estimate is a projection at a point in time, not a binding quote, so a legitimate change in the care is not a violation.

The move when you can see a divergence coming is to reissue, not to absorb it silently. A refreshed estimate that captures the new scope resets the window and documents why the numbers moved 2Ref 2Centers for Medicare & Medicaid Services (2026).No Surprise Billing.That the No Surprises Act requires good-faith estimates for self-pay and uninsured patients and creates the patient-provider dispute-resolution process available when a bill exceeds the estimate, with CMS hosting the implementing guidance.. Whether the reader is holding the insured gfe question or a self-pay estimate, the principle is the same: when the expected charges change materially, issue a new estimate and keep the old one, so the trail explains the difference rather than hiding it.

Why estimate discipline is billing discipline

The habit that keeps estimates honest is the same habit that keeps claims defensible. An estimate you built from real codes and real fees, and can reconstruct later, is protection against a dispute; the identical discipline on the claims side is protection against something much larger. The two are not separate skills — they are one relationship with your own numbers.

That larger exposure is the False Claims Act, which reaches knowingly false figures on claims to federal programs with treble damages and per-claim penalties, and where "knowingly" includes reckless disregard 3Ref 3U.S. Department of Justice (2026).The False Claims Act.That the False Claims Act imposes treble damages and per-claim penalties for knowingly false figures on federal claims, with 'knowingly' reaching reckless disregard, framing estimate documentation as billing self-defense.. An estimate is not a federal claim, but a practice that lowballs estimates is a practice that is careless with numbers, and carelessness is exactly what that law punishes elsewhere. Honest, itemized math is cheap insurance across every part of the practice at once, from the estimate through the NSA for office practice to the claim.