How the checks work

Nine fixed checks, each written in code. This page says what each one does, when it stays quiet, and what data it uses.

Every finding comes from one of these checks. The AI only reads your bill into structured data; fixed, tested rules decide every finding. Separately, it can give a general definition of a billing code when you ask. It never decides whether something is a problem.

The nine checks

1. Duplicate charge
What it checks
Two or more lines with the same code, date of service, modifiers, units, unit price and charge.
When it stays quiet
Lines with no code, no date, or a charge of zero or less are never compared.
How sure it is
Medium. Some services really are done twice.
Made-up example
Code 80053 appears twice on March 2, 1 unit, $40.00 each. One extra copy: $40.00 in question.
2. Math error
What it checks
A line whose charge is more than its units multiplied by its unit price.
When it stays quiet
Lines with no unit price or a negative one. A charge below units times price is not flagged.
How sure it is
High. It is arithmetic.
Made-up example
2 units at $50.00 should be $100.00, but the charge is $130.00. $30.00 in question.
3. Date outside the service range
What it checks
A line dated before the start or after the end of the service dates printed on the statement.
When it stays quiet
No check if the statement has no dates, or if its start date is after its end date.
How sure it is
High.
Made-up example
The statement covers March 1 to March 3, but one line is dated March 9. That line's full charge is in question.
4. Possible unbundling
What it checks
Two lines on the same date that a Medicare NCCI procedure-to-procedure edit says should not be billed together, because one is normally included in the other.
When it stays quiet
When the edit allows a modifier and the bundled line carries one of 59, XE, XP, XS or XU, or modifier 25 on an evaluation and management (E/M) code (99202 to 99499). No check for hospital (facility) edits.
How sure it is
High when the edit allows no modifier at all. Medium when a modifier could have been used.
Made-up example
An edit lists code A as the main service and code B as included in it. Both are billed on the same day, and B has no modifier. B's charge is in question.
5. More units than Medicare expects
What it checks
The units billed for one code on one date, added across all lines, are above Medicare's medically unlikely edit (MUE) for that code.
When it stays quiet
A total equal to the limit. Codes with no MUE. Lines with no code or date.
How sure it is
High for date-of-service edits. Medium when the edit applies per claim line, since adding lines is less certain.
Made-up example
A code has a limit of 1 unit per day and is billed at 3 units. The 2 extra units at their unit price are in question.
6. Price far above Medicare
What it checks
A unit charge for a CPT or HCPCS code that is more than 5 times the Medicare Physician Fee Schedule price for Los Angeles (locality 18), office setting.
When it stays quiet
Exactly 5 times does not fire. Codes with no Medicare price, services not on the schedule, and lines with no code.
How sure it is
Medium. Medicare is a benchmark, not what your provider agreed to with your plan. The 5-times line is our own choice, not a legal limit.
Made-up example
Medicare's price for a service is $20.00 and the bill charges $150.00. That is over $100.00 (5 times), so the $130.00 difference is in question.
7. Vague charge
What it checks
A line with no code whose description is a generic word (misc, miscellaneous, other, supplies, services, pharmacy, general), or an uncoded line over $100.00.
When it stays quiet
Any line that has a code. Lines with a charge of zero or less.
How sure it is
Medium.
Made-up example
A line reads 'Misc supplies' with no code and a charge of $45.00. The full $45.00 is in question.
8. Denied by insurance but billed to you
What it checks
Your insurer's explanation of benefits (EOB) shows a denial reason for a service, and the bill still asks you to pay for the same code and date.
When it stays quiet
Needs an EOB. EOB lines without a code or date are not matched. A line where you owe nothing.
How sure it is
High. A denial can be correct, so read the denial reason on your EOB.
Made-up example
The EOB denies a code on April 5 and the bill still shows $75.00 owed by you. $75.00 is in question.
9. Bill asks for more than the EOB says you owe
What it checks
The bill's patient amount for a service is higher than the patient responsibility on the EOB for the same code and date.
When it stays quiet
Needs an EOB. Only when exactly one bill line and one EOB line match. Denied lines (a separate check). Lines where either amount is unknown.
How sure it is
Medium. The bill and the EOB are made at different times, so the gap may be a payment not yet shown.
Made-up example
The bill says you owe $120.00 and the EOB says your share is $50.00. The $70.00 difference is in question.

Data and versions

All of it is public CMS data.

NCCI procedure-to-procedure edits: practitioner edits only (edit set 1), 2026 Q4 release.
NCCI medically unlikely edits: practitioner services table, 2026 Q4 release.
Medicare Physician Fee Schedule relative value units: RVU26A.
Locality: Los Angeles, Medicare administrative contractor 01182, locality 18. Other places are not covered.
Conversion factor: the standard one, not the one for qualifying alternative payment model participants.
Setting: office (non-facility) prices, with the 26 and TC modifier rows where they exist.

What it does not do

Price and quantity checks only cover services that are on the Medicare Physician Fee Schedule. Hospital facility charges, such as a room fee, are outside them.
We tested the checks on made-up bills written alongside the rules, so the results show agreement with our own expectations, not real-world accuracy.
A finding is a reason to ask a question, not proof of a mistake, and not legal advice.

How the checks work

Nine fixed checks, each written in code. This page says what each one does, when it stays quiet, and what data it uses.

The nine checks

1. Duplicate charge

What it checks: Two or more lines with the same code, date of service, modifiers, units, unit price and charge.
When it stays quiet: Lines with no code, no date, or a charge of zero or less are never compared.
How sure it is: Medium. Some services really are done twice.
Made-up example: Code 80053 appears twice on March 2, 1 unit, $40.00 each. One extra copy: $40.00 in question.

2. Math error

What it checks: A line whose charge is more than its units multiplied by its unit price.
When it stays quiet: Lines with no unit price or a negative one. A charge below units times price is not flagged.
How sure it is: High. It is arithmetic.
Made-up example: 2 units at $50.00 should be $100.00, but the charge is $130.00. $30.00 in question.

3. Date outside the service range

What it checks: A line dated before the start or after the end of the service dates printed on the statement.
When it stays quiet: No check if the statement has no dates, or if its start date is after its end date.
How sure it is: High.
Made-up example: The statement covers March 1 to March 3, but one line is dated March 9. That line's full charge is in question.

4. Possible unbundling

What it checks: Two lines on the same date that a Medicare NCCI procedure-to-procedure edit says should not be billed together, because one is normally included in the other.
When it stays quiet: When the edit allows a modifier and the bundled line carries one of 59, XE, XP, XS or XU, or modifier 25 on an evaluation and management (E/M) code (99202 to 99499). No check for hospital (facility) edits.
How sure it is: High when the edit allows no modifier at all. Medium when a modifier could have been used.
Made-up example: An edit lists code A as the main service and code B as included in it. Both are billed on the same day, and B has no modifier. B's charge is in question.

5. More units than Medicare expects

What it checks: The units billed for one code on one date, added across all lines, are above Medicare's medically unlikely edit (MUE) for that code.
When it stays quiet: A total equal to the limit. Codes with no MUE. Lines with no code or date.
How sure it is: High for date-of-service edits. Medium when the edit applies per claim line, since adding lines is less certain.
Made-up example: A code has a limit of 1 unit per day and is billed at 3 units. The 2 extra units at their unit price are in question.

6. Price far above Medicare

What it checks: A unit charge for a CPT or HCPCS code that is more than 5 times the Medicare Physician Fee Schedule price for Los Angeles (locality 18), office setting.
When it stays quiet: Exactly 5 times does not fire. Codes with no Medicare price, services not on the schedule, and lines with no code.
How sure it is: Medium. Medicare is a benchmark, not what your provider agreed to with your plan. The 5-times line is our own choice, not a legal limit.
Made-up example: Medicare's price for a service is $20.00 and the bill charges $150.00. That is over $100.00 (5 times), so the $130.00 difference is in question.

7. Vague charge

What it checks: A line with no code whose description is a generic word (misc, miscellaneous, other, supplies, services, pharmacy, general), or an uncoded line over $100.00.
When it stays quiet: Any line that has a code. Lines with a charge of zero or less.
How sure it is: Medium.
Made-up example: A line reads 'Misc supplies' with no code and a charge of $45.00. The full $45.00 is in question.

8. Denied by insurance but billed to you

What it checks: Your insurer's explanation of benefits (EOB) shows a denial reason for a service, and the bill still asks you to pay for the same code and date.
When it stays quiet: Needs an EOB. EOB lines without a code or date are not matched. A line where you owe nothing.
How sure it is: High. A denial can be correct, so read the denial reason on your EOB.
Made-up example: The EOB denies a code on April 5 and the bill still shows $75.00 owed by you. $75.00 is in question.

9. Bill asks for more than the EOB says you owe

What it checks: The bill's patient amount for a service is higher than the patient responsibility on the EOB for the same code and date.
When it stays quiet: Needs an EOB. Only when exactly one bill line and one EOB line match. Denied lines (a separate check). Lines where either amount is unknown.
How sure it is: Medium. The bill and the EOB are made at different times, so the gap may be a payment not yet shown.
Made-up example: The bill says you owe $120.00 and the EOB says your share is $50.00. The $70.00 difference is in question.

Data and versions

All of it is public CMS data.

NCCI procedure-to-procedure edits: practitioner edits only (edit set 1), 2026 Q4 release.

NCCI medically unlikely edits: practitioner services table, 2026 Q4 release.

Medicare Physician Fee Schedule relative value units: RVU26A.

Locality: Los Angeles, Medicare administrative contractor 01182, locality 18. Other places are not covered.

Conversion factor: the standard one, not the one for qualifying alternative payment model participants.

Setting: office (non-facility) prices, with the 26 and TC modifier rows where they exist.

What it does not do

Price and quantity checks only cover services that are on the Medicare Physician Fee Schedule. Hospital facility charges, such as a room fee, are outside them.

We tested the checks on made-up bills written alongside the rules, so the results show agreement with our own expectations, not real-world accuracy.

A finding is a reason to ask a question, not proof of a mistake, and not legal advice.