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CMS-1500 Claim Checker

Enter a claim box by box and find the errors that get claims rejected or denied, before the payer does. Free, and nothing leaves your browser.

Payer and patient

Payer type

Box 1a: insured's ID

Box 2: patient name

Box 3: patient birth date

Box 3: sex

Box 21: ICD indicator

Box 21: diagnoses A to L

Box 22: resubmission

Resubmission code

Original reference number

Box 24: service lines

Line 1: 24A from

24A to

24B POS

24D CPT/HCPCS

24D modifiers

24E pointer

24F charges ($)

24G units

24J rendering NPI

Line 2: 24A from

24A to

24B POS

24D CPT/HCPCS

24D modifiers

24E pointer

24F charges ($)

24G units

24J rendering NPI

Billing provider

Box 25: federal tax ID

Box 28: total charge ($)

Box 33: billing provider name

Box 33a: billing NPI

Box 31: signed, or "Signature on File"

What the Checker Looks For

Box	Check	Why it gets claims rejected
1a	ID present; Medicare MBI format (11 characters)	Wrong or old IDs reject at the clearinghouse
3	Birth date valid, sex entered	Mismatch with the payer's records
21	ICD indicator 0; each code valid and billable for the date of service; no gaps or repeats	Invalid or incomplete codes deny as CO-16 or CO-11
22	Blank on original claims; 7 or 8 always with the original claim number	Missing claim number rejects
24A	Dates present, not in the future, in order; timely filing	Late claims deny as CO-29
24B	Valid CMS place of service code	Invalid POS rejects
24D	Code exists; Medicare status; 26/TC allowed; up to 4 modifiers; duplicates; modifier 25 with a same-day procedure	Bundling and duplicate denials
24E	1 to 4 letters A to L that point to real diagnoses	Pointer errors reject
24G	Whole units; practitioner MUE per day	Units over the MUE deny
24J, 33a	NPI check digit	A mistyped NPI rejects
25, 28	9-digit tax ID; total equals the lines	Totals that do not add up reject

How to Use It

Copy the claim into the form, box by box. Use the diagnosis letters (A to L) in box 24E, not the codes.
Press Check this claim. Errors will likely reject or deny; warnings need a second look.
Fix each item and check again until you see no errors.
Not sure how to fill a box? See our CMS-1500 instructions, box by box.

Common Rejections This Prevents

Invalid or non-billable ICD-10 codes, including codes that changed on October 1, 2026.
Box 22 errors, such as frequency code 7 with no original claim number.
Medicare status I codes, such as consultation codes 99242 to 99245, which Medicare does not accept.
Units over the MUE, which deny automatically.
Mistyped NPIs, caught by the check digit.
For denials you already have, look up the reason in our denial code guides.

Sources: NUCC 1500 Health Insurance Claim Form Reference Instruction Manual, version 13.0 (July 2025); CMS NPI check digit (Luhn formula with prefix 80840); CMS Medicare Beneficiary Identifier format; CMS Place of Service Code Set; CDC/CMS ICD-10-CM FY2027 files; CMS MUE tables (October 2026); CMS CY 2026 Physician Fee Schedule RVU file (status, global days, PC/TC).

Frequently Asked Questions

What is a claim scrubber?

A claim scrubber checks a claim for errors before you send it, so the payer does not reject or deny it. It looks for missing fields, invalid codes, bad diagnosis pointers, unit limits and modifier problems. This free checker runs the most common CMS-1500 checks in your browser.

What does this CMS-1500 checker look at?

It checks the insured ID (including the Medicare MBI format), patient details, every ICD-10 code for the date of service, box 22 resubmission rules, place of service codes, CPT and HCPCS codes, Medicare code status, modifiers 26 and TC, diagnosis pointers, MUE unit limits, duplicate lines, modifier 25 with a procedure, NPI check digits, the tax ID and the total charge.

What does "payer claim control number is required" mean?

It is a rejection you get when box 22 (or CLM05-3 on an 837P) says 7 or 8 but the original claim number is missing. Add the payer's claim number from the first claim's remittance in the right side of box 22 (REF*F8 electronically).

Should I put 1 in box 22 for a new claim?

No. The NUCC instructions say box 22 is not for original claims. Leave it blank. Use 7 to replace a claim or 8 to void it, with the original claim number.

Does this checker catch NCCI edits?

Not yet. It does not check NCCI procedure-to-procedure pairs, payer policies, prior authorization or medical necessity. It catches the data and format errors that cause most front-end rejections.

Hassan Raza Awan, Founder of LegitMedBilling & IT Solutions

Written by Hassan Raza Awan

Founder — LegitMedBilling & IT Solutions

Hassan has 4+ years of hands-on U.S. medical billing experience — working claims, denials, credentialing, and payer follow-up for practices across the United States. Every guide he publishes is written from real remittances and payer behavior, not theory.

Timed therapy codes on the claim? Work out the units with our 8 minute rule calculator. Surgical code on the claim? Check its global days with our global period calculator.

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