Methodology & Sources
The core calculation
EOBCheck's reconciliation is arithmetic, not a legal judgment. The formula behind every result:
How the result is flagged
Two additional checks run on the Full Report tier: whether the provider's total billed amount matches the EOB's total billed amount, and whether the EOB's own math is internally consistent (allowed amount minus insurance paid should equal patient responsibility).
The Good Faith Estimate check
If a Good Faith Estimate amount is entered, EOBCheck checks whether the bill exceeds it by $400 or more — the federal threshold for a Patient-Provider Dispute Resolution filing under the No Surprises Act. This is a mechanical threshold check, not a determination of legal eligibility, which depends on additional requirements (insurance status, filing windows) outside what a calculator can verify.
Known limitations
A flagged variance is a starting point for a conversation, not proof of an error. Common legitimate reasons a variance can appear even when nothing is actually wrong:
- The bill and EOB reflect different dates of service
- Multiple claims were combined into or split across one bill
- Multiple providers billed separately for the same visit
- A claim is still pending or being reprocessed
- A partial payment was already made and not yet reflected
- Secondary insurance hasn't finished processing
- An out-of-network situation applies different rules
- The claim was corrected or resubmitted after the bill was printed
EOBCheck's checklist and generated letter are written to account for this — asking for a written explanation rather than asserting the provider is wrong.
Primary sources
See also our About page and EOB Glossary.