Documentation Errors That Cause Claim Denials (and How CDI Prevents Them)

A claim can be coded correctly, for a service that really happened, and still be denied or recovered later, because the note didn’t prove it. For practices and hospitals, that’s lost revenue, extra rework, and appeals that eat into clinicians’ time.

This guide covers the documentation errors that cause claim denials, what the data shows, how clinical documentation improvement (CDI) prevents them, and practical ways to reduce denials in your organization.

Claims are denied often: HealthCare.gov insurers denied nearly 1 in 5 in-network claims in 2023.

• Private insurance: A KFF analysis found that insurers selling HealthCare.gov plans denied 19% of in-network claims in 2023. Administrative reasons accounted for 21% of in-network denials, and lack of prior authorization or referral for 9%. Only about 6% were denied for lack of medical necessity.
• Medicare: CMS estimated a Medicare fee-for-service improper payment rate of 7.66% ($31.70 billion) in fiscal year 2024, falling to 6.55% ($28.83 billion) in fiscal year 2025.

Documentation causes claim denials because payers pay for what the record proves, not the claim.

CMS reports that the vast majority of Medicare improper payments happen when a reviewer can’t confirm a payment was proper because of insufficient documentation. CMS also notes that insufficient documentation is generally not a sign of fraud.

In other words, the care was often delivered and the code was often right. The note simply didn’t show it. That’s good news, because documentation problems are fixable.

Clinical documentation improvement (CDI) makes medical records accurate, complete, and specific.

CDI programs review medical records, usually while the patient is still in care or before a claim is billed, to make sure the documentation reflects how sick the patient is and what care they received. When something is unclear or missing, a CDI specialist sends the clinician a query asking them to clarify.

Done well, CDI does more than protect revenue:

• Fewer denials and recoupments, because the record supports the claim
• More accurate coding, because diagnoses are documented with the right specificity
• Better data for quality reporting and care coordination
• Less rework for clinicians and billing teams later

Most of the mistakes below are exactly what CDI is designed to catch.

The most common mistakes are missing notes, unclear medical necessity, and unsupported visit levels.

1. Is the documentation missing or incomplete?

Missing or incomplete documentation can’t support payment, so the claim may be denied or recovered.

The simplest denial reason is also among the most common: no documentation, or incomplete documentation, for the date of service. CMS’s review contractors count claims with missing records as improper payments.

Fix: Close notes promptly, track open encounters daily, and make sure the full record (including results and orders) is available when requested.

2. Is medical necessity documentation missing?

Medical necessity documentation explains why a service was needed; without it, claims get denied.

A note that lists what was done, without the clinical reasoning, leaves the reviewer guessing. See how to write medical necessity documentation below.

3. Does the documentation support the level of service billed?

Documentation must support the level of service billed; a mismatch either way causes errors.

For evaluation and management (E/M) visits, the documented complexity or time must support the level billed. CMS’s review data has identified E/M level errors, both upcoding and downcoding, as leading causes of Medicare Part B improper payments.

Fix: Document medical decision-making or total time clearly, and audit a sample of E/M visits regularly.

4. Are orders, signatures, and certifications in place?

Missing orders, signatures, or certifications can invalidate an otherwise complete record.

Many services require a signed order, and some require specific certifications. In home health and hospice, for example, CMS’s 2025 review highlighted missing physician certifications and missing face-to-face encounter documentation among the top causes of errors.

Fix: Check orders and signatures before billing, and track certification and recertification deadlines.

5. Does the diagnosis coding match the documentation?

Diagnosis coding must match the documentation, at the level of specificity the code requires.

Vague documentation ("diabetes," "back pain") can force unspecified codes that payers may not accept for certain services, while codes that go beyond what’s documented won’t survive review.

Fix: Document specificity (type, location, laterality, severity) and query clinicians when the note doesn’t support the most accurate code.

6. Was prior authorization obtained and documented?

Prior authorization must be obtained and documented, or the service is commonly denied.

In KFF’s analysis, lack of prior authorization or referral accounted for 9% of in-network denials on HealthCare.gov plans.

Fix: Verify authorization requirements before scheduling, and keep the authorization number and approval in the record.

7. Are notes copied forward without updates?

Notes copied forward without updates can carry outdated findings and undermine the whole record.

Copying text from previous notes saves time, but if the findings, plan, or history aren’t updated, the note may not reflect the visit, and reviewers may question whether the service was performed as billed.

Fix: Allow copy-forward only for stable history, and require clinicians to update the assessment and plan every visit.

8. Was the note completed promptly?

Notes completed promptly are more complete and accurate than notes written long after the visit.

Delayed documentation increases the chance of missing details, and late entries can raise questions during review. Many organizations set internal deadlines for closing notes.

Fix: Close notes the same day where possible, and follow your organization’s policy for late entries and addenda.

Medical necessity documentation links each service to the patient’s symptoms and diagnosis.

Medical necessity documentation answers one question for the reviewer: why did this patient need this service, now? To make that clear:

1. State the presenting problem: symptoms, duration, and severity in the patient’s words and your findings.
2. Document the relevant findings: exam, test results, and history that support your assessment.
3. Connect the service to the diagnosis: explain why the test, procedure, or referral was ordered.
4. Note what’s changed: for follow-ups and repeat services, document progress or decline that justifies continuing care.
5. Check payer coverage criteria: for Medicare, national and local coverage determinations (NCDs and LCDs) list the documentation certain services require.

You can reduce documentation-related claim denials with templates, pre-bill checks, and audits.

1. Standardize templates for common visit types, with prompts for medical necessity and required elements.
2. Run pre-bill checks for missing signatures, orders, authorizations, and open notes.
3. Audit a sample of claims each month, with feedback to clinicians.
4. Build a clinical documentation improvement (CDI) program, where CDI specialists and coders query clinicians when documentation is unclear.
5. Track denial reasons so you fix the root cause, not just the individual claim.
6. Reduce documentation burden, since rushed notes are more likely to miss key details.

AI documentation tools can help clinicians capture complete notes, but every note needs review.

AI scribes can turn a clinical conversation into a structured draft note, which can make it easier to capture the history, findings, and reasoning that support a claim. But AI doesn’t guarantee payment, and clinicians remain responsible for the accuracy of every note.

HosTalky AI Scribe turns clinical conversations and verbal summaries into structured notes you review and edit before you approve them. Evaluating it for your practice? Book a demo.