Reference · 2026 edition
Code & modifier directory
15 of the codes and modifiers that generate the most billing questions — and the most denials. Each entry covers the threshold that defines it, the documentation that keeps it paid, and the specific ways payers reduce or refuse it.
Written in our own words as billing commentary. CPT is a registered trademark of the American Medical Association; official code descriptors are not reproduced here.
E/M office visits
Established and new patient office and outpatient visit levels — the highest-volume, highest-scrutiny codes in most practices.
- 99213Low audit risk
Level-3 established patient office visit
20–29 minutes total time · Low MDM
Billing rules - 99214Elevated audit risk
Level-4 established patient office visit
30–39 minutes total time · Moderate MDM
Billing rules - 99215High audit risk
Level-5 established patient office visit
40–54 minutes total time · High MDM
Billing rules - 99203Moderate audit risk
Level-3 new patient office visit
30–44 minutes total time · Low MDM
Billing rules - 99204Elevated audit risk
Level-4 new patient office visit
45–59 minutes total time · Moderate MDM
Billing rules
Psychotherapy
Diagnostic evaluation, individual and family psychotherapy, and the session-length distinctions that drive behavioral health denials.
- 90791Moderate audit risk
Psychiatric diagnostic evaluation without medical services
No time band; one unit per evaluation · Diagnostic assessment
Billing rules - 90834Low audit risk
Individual psychotherapy, 45-minute session
38–52 minutes of therapy time · Standard session
Billing rules - 90837Elevated audit risk
Individual psychotherapy, 60-minute session
53 minutes or longer of therapy time · Extended session
Billing rules - 90847Moderate audit risk
Family psychotherapy with the patient present
Approximately 50 minutes · Family session, patient present
Billing rules
Add-on services
Prolonged services, visit complexity, and other codes that are only reportable alongside a primary service.
- 90833Elevated audit risk
Psychotherapy add-on to an E/M visit, 30 minutes
16–37 minutes of psychotherapy time · Add-on to E/M
Billing rules - 99417High audit risk
Prolonged office or outpatient service, each 15 minutes
Each additional 15 minutes · Add-on, time-based
Billing rules - G2211Moderate audit risk
Visit complexity add-on for continuing care
One unit per qualifying visit · Add-on, relationship-based
Billing rules
Modifiers
The two-character suffixes that most often decide whether a correctly coded claim is paid or bundled away.
- Modifier 25High audit risk
Significant, separately identifiable E/M on the same day as a procedure
Appended to the E/M line · Documentation-dependent
Billing rules - Modifier 59High audit risk
Distinct procedural service
Appended to the secondary procedure line · Edit override
Billing rules - Modifier 95Moderate audit risk
Synchronous telehealth via real-time audio and video
Appended to the service line · Delivery indicator
Billing rules
Reference only — verify against your payer
Rules described here reflect general current guidance and are typical, not universal. Coverage, modifier requirements, and prolonged-service handling vary by payer, plan, state, and provider credentials. Confirm current payer policy before billing.
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