Billing answers that always show where they came from
Nineteen friendly, free tools for billing teams and physicians — built from the eCFR, the Federal Register and CMS’s own manuals. Ask a question below and see exactly which rule the answer rests on.
Three questions behind most denials
Pick the one in front of you. Each goes straight to the tool built for it — no form, no funnel, no account.
“How long do we have?”
Filing windows by programme, prior authorization decision limits by urgency, and the ESRD coordination period — each showing how the days are counted, not just the number.
Deadline tools →“Which code or modifier?”
ICD-10-CM validity against the date of service, the HCPCS Level II modifier set exactly as CMS publishes it, plus dental, telehealth and anesthesia checks.
Coding tools →“Who pays first?”
Payer order across Medicare, Medicaid, TRICARE, VA, COBRA and dependent children — and what the patient is actually left owing.
Coverage tools →Nineteen tools, one standard of evidence
Each answers a single question a billing team actually has to answer — and names the document behind the answer.
Medical Billing Modifiers
Every HCPCS Level II modifier from the CMS October 2026 file, plain-English CPT modifier guides, and the comparisons that cause denials.
384 modifiers · 23 guides →Timely Filing Limits
Medicare, state Medicaid and published payer defaults, with a file-by date calculator that shows how the days are counted.
51 programme cards →Prior Authorization Deadlines
How long the payer has to decide, standard and expedited, scoped to exactly what the 2026 federal rule covers.
8 programme types →Who Pays First?
Primary versus secondary coverage, a Medicare secondary payment calculator, and the ESRD 30-month coordination period.
14 combinations →ICD-10 Code Search
Check a diagnosis code against the date of service, and explore what FY2027 added, split or deleted.
FY2027 explorer →Patient Responsibility Calculator
Deductible, coinsurance, copay and out-of-pocket maximum, applied in the order plans actually apply them.
Shows the working →Denial Code Lookup
Search CARC and related denial codes, with plain-English explanations and step-by-step resolution guides.
171 denial codes →PA Check
Whether a CPT or HCPCS code may require prior authorization, by payer and specialty.
Payer & specialty →Policy Peek
Look into payer policy positions behind a coverage decision before you write the appeal.
Policy reference →CPT Coding Assistant
Pull the related ICD-10 codes, modifiers, billing rules and audit alerts for a CPT code, without a login.
Coding reference →Telehealth Billing Code Checker
Place of service and modifier checks for virtual visits, including the POS 02 versus POS 10 distinction.
POS & modifiers →Dental Procedure Code Lookup
Dental procedure references for practices that bill both medical and dental.
Procedure reference →Anesthesia Billing Units Calculator
Base units, time units and modifying factors worked through step by step.
Unit calculation →Practice Revenue Leakage Analyzer
Work through where denials are costing the practice, and what is realistically recoverable.
Worksheet →RCM Cost Truth Calculator
What revenue cycle work actually costs per claim, stated openly instead of sold.
Cost per claim →Physician Hourly Rate Calculator
Translate compensation into an hourly figure you can compare against the time a task takes.
Rate calculation →NPI Provider Lookup
Search the CMS NPPES registry for a provider’s name, taxonomy, practice address and OIG exclusion status before you bill.
Provider check →Audit Guard
Check documentation exposure before a payer does.
Documentation review →SuperBill Creator
Assemble a clean, printable superbill for a patient encounter.
Printable output →Showing all 19 tools.
Kept current with the source files
When CMS publishes, the tools follow. Each card says which release it was checked against.
Medical Billing Modifiers
Rebuilt against the CMS October 2026 HCPCS Level II file.
September 2026ICD-10 Code Search
FY2027 addenda loaded, with an explorer for added, split and deleted codes.
September 2026Prior Authorization Deadlines
Scoped to the 2026 federal rule, including what it excludes.
September 2026Timely Filing Limits
51 programme cards checked against current published limits.
We read the regulation, not a summary of it
And where a rule depends on the plan, the state or your contract, the tool says so instead of inventing a single national answer.
- 01Electronic Code of Federal RegulationsTitles 42, 45 and 29, read at section level — including 42 CFR 424.44 for filing and 42 CFR 411 for coordination of benefits.
- 02Federal Register, via govinfoFinal rules read in full, including the 2026 interoperability and prior authorization rule.
- 03United States CodeUsed where the statute and the regulation diverge — and we say so when they do.
- 04CMS manuals, Pub. 100-04 and Pub. 100-05Claims processing and Medicare Secondary Payer, with CMS’s own worked examples used to validate our calculators.
- 05Official CMS code set releasesQuarterly HCPCS Level II files and annual ICD-10-CM addenda, dated inside the tool.
- 06Medicare.gov and Medicaid.govProgramme and state plan detail, cited per card rather than generalised.
What we will never do
- Publish a figure without a source.
- Republish licensed code descriptions we have no right to reproduce.
- Present a plan-specific rule as a national one.
- Claim certainty where the evidence is mixed — “not verified” is an allowed answer.
- Sell you a service. The tools are the whole product.
Three steps, no account
The same simple sequence behind every tool on the site.
Choose your question
Deadline, code, modifier, payer order or patient cost. Each tool does one job properly rather than five badly.
Enter what you know
A code, a date of service, a payer type. Everything runs locally in your browser — nothing is stored or sent anywhere.
Follow the citation
Every answer carries its source, so you can verify the rule before you bill, write off or appeal.
Published when a rule actually changes
Deletions, splits, bundling edits and audit exposure — written for the person who has to rebill.
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Modifier 25 & Same-Day Injections: 2026 Audit Guide
By Sarah Callahan ·By Sarah Callahan — Reviewed by Eman Zahra — Last updated: August 2026 Educational disclaimer: This article is general educational…
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ICD-10 G35 Deleted: Why MS Claims Are Denied (2026)
By Eman Zahra ·By Eman Zahra | Last updated August 20, 2026 This article is for general educational purposes only. It is not…
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AI Prior Auth Denial Appeals: Ophthalmology Guide
By Danish William ·Bottom line: If your ophthalmology practice received a prior authorization denial you suspect was algorithm-driven, don’t start by writing a…
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PCI Add-On Codes 92921–92929 Deleted: 2026 Billing Guide
By Eman Zahra ·If your charge master still has 92921, 92925, or 92929 on it, every claim carrying one of those codes since…
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The Complete CPT Codes Guide for Medical Billing in 2026
By Danish William ·I have sat across the table from physicians who were brilliant clinicians — and completely baffled by a denial letter.…
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CPT 55700 Deleted for 2026: Which Code Replaces It?
By Eman Zahra ·CPT 55700 is gone. Effective January 1, 2026, the code is deleted, and it cannot be used for any 2026…
Short answers, with the rule attached
The six we are asked most. Each one names its source, the same as every tool does.
How long do I have to file a Medicare claim?
One calendar year from the date of service. It is set in regulation rather than by your contractor, and there are four narrow exception categories for administrative error. Medicaid and commercial limits are set separately, by the state plan or your participation agreement.
42 CFR 424.44 · Medicare Claims Processing Manual (Pub. 100-04), ch. 1 §70Does every payer have to decide a prior authorization in seven days?
No — and this is widely misreported. The 2026 federal timeframes apply to specific programmes, cover items and services excluding drugs, and did not change the timeframes for marketplace QHP issuers. Drugs follow their own rules entirely. Our tool splits this out by programme rather than quoting one number.
CMS-0057-F, Federal Register — read in full via govinfoWhen should I use modifier 59 instead of an X modifier?
Only when none of XE, XS, XP or XU describes the situation. CMS asks for the more specific modifier wherever one fits, so 59 is properly a last resort rather than a default.
CMS MLN1783722 · National Correct Coding Initiative Policy Manual, ch. 1My patient has Medicare and still works — who pays first?
For age-based entitlement it turns on the employer’s size: with 20 or more employees the group health plan generally pays first; with fewer than 20, Medicare generally pays first. Multi-employer plans are treated separately, so check the specific rule rather than assuming.
42 CFR 411 subpart F · Medicare Secondary Payer Manual (Pub. 100-05), ch. 1How long is the ESRD coordination period?
Thirty months. Worth knowing: the regulation at 42 CFR 411.162(c) still reads 12 and 18 months, because the thirty-month period comes from the statute rather than from that regulation being updated. Our tool cites the statute for this one, and says why.
42 U.S.C. 1395y(b)(1)(C) · compare 42 CFR 411.162(c)Are the tools really free — what is the catch?
There isn’t one. There is no account, no card, no usage limit and no service being sold behind them. The tools run in your browser, so what you look up is never stored or sent anywhere. We publish an editorial policy and a corrections policy so you can hold us to that.
Editorial policy · Corrections policyFour promises we keep
They decide what gets published here, and what does not.
Cited, or not published
Every rule names the document behind it, and the date that document was read.
Honest about limits
Plan, state and contract variation is labelled — never averaged into a false single answer.
Private by design
The tools keep no record of what you look up. They run entirely in your browser.
Corrected in public
Errors are fixed and logged under a published corrections policy.
You shouldn’t need a subscription to read a rule
Written for the person who signs the claim: the deadline you can put in a diary, the modifier CMS actually describes, the payer that should have paid first — and the citation to take into the appeal.
Start with the toolsWhere practices reach for it
- Before a write-off
- Confirm the filing window and how the days are counted.
- Before appending a modifier
- Check what CMS describes, and whether a more specific one exists.
- Before billing secondary
- Establish payer order and the rule that sets it.
- Before quoting a patient
- Work the cost share through in the order the plan applies it.
- Cost
- Free — no account, no card, no gated downloads and no sales call.
Spotted an error, or need a rule we have not covered?
Tell us and we will look it up. Corrections are published, not quietly edited.
Find the rule. Then bill with confidence.
Nineteen free tools and a growing library of guides — every answer traceable to the document it came from.