CPT Code 99359Complete Billing & Coding Guide (2026)Prolong serv without contact add
About CPT 99359
CPT 99359 is a Current Procedural Terminology code in the E/M category maintained by the American Medical Association. The CMS short descriptor reads "Prolong serv w/o contact add". For the full AMA long descriptor and clinical guidance, refer to the current CPT code manual.
Add-on codes cannot be billed alone and inherit their global period from the primary procedure. Payer scrubbers will reject add-on codes submitted without a valid base code on the same claim.
When billing 99359 with a procedure on the same day, use modifier 25 to indicate a significant, separately identifiable E/M service. Documentation must support the separate work, including a distinct chief complaint or HPI section if applicable.
Code Properties
RVU Breakdown
Every CPT code’s Medicare payment is calculated from three Relative Value Unit components: physician work, practice expense, and malpractice. Together they multiply by the conversion factor to produce the payment amount.
Payment = Total RVU × Conversion Factor ($33.4009) × Geographic Adjustment (GPCI). National averages shown. Actual payment varies by locality.
Medicare Payment by State
Medicare adjusts payment by locality based on GPCI (Geographic Practice Cost Index). Higher cost-of-living areas like California and New York pay more. Rural states pay less. Top 12 states shown.
Showing top 12 of 53 states. Full locality data available in CMS PFS Locality file.
NCCI Bundling Edits
10 pairsThese codes trigger National Correct Coding Initiative edits when billed with 99359. An indicator of 0 means the pair cannot be unbundled. Indicator 1 means modifier 59 or X-modifiers may allow separate billing with supporting documentation.
Billing 99359 alongside a bundled code without the correct modifier generates CARC 97 denials. Payers often flag these as audit risks. Document medical necessity for the separate service and apply modifier 59 or the appropriate X-modifier (XE, XS, XP, XU) only when clinically justified.
Misuse of Column Two code with Column One code
Misuse of Column Two code with Column One code
Misuse of Column Two code with Column One code
CPT Manual or CMS manual coding instruction
CPT Manual or CMS manual coding instruction
Misuse of Column Two code with Column One code
CPT Manual or CMS manual coding instruction
CPT Manual or CMS manual coding instruction
Standards of medical/surgical practice
CPT Manual or CMS manual coding instruction
E/M-with-procedure CO-97 denials are usually a modifier 25 documentation problem, not a bundling truth. Distinct chief complaint, distinct HPI, distinct A/P sections in the chart make the modifier 25 defensible. We audit every E/M line billed with a same-day procedure before submission.
Applicable Modifiers
Modifiers commonly paired with 99359 based on its category. Apply only when the clinical circumstance warrants. Incorrect modifier use is a top audit target.
Modifier 25 on E/M plus same-day procedure is the most-audited modifier in physician billing. UnitedHealthcare, Anthem, and several BCBS plans run automated post-pay review on these claims. We audit every modifier 25 application against the chart before submission.
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Wrong modifier, missing documentation, bundling without justification, stale ICD-10 linkage: these are the silent revenue killers on E/M claims. Our AAPC-certified team audits your last 90 days of 99359 claims, surfaces the recoverable dollars, and appeals them. Free, no obligation.
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Related CPT Codes
Codes in the same family as 99359
Specialty billing guides
CPT 99359 is among the top codes profiled in these specialty billing guides.
Everything about CPT 99359
What does CPT code 99359 cover?
CPT 99359 is a Current Procedural Terminology code in the E/M category maintained by the American Medical Association. The CMS short descriptor reads "Prolong serv w/o contact add". For the full AMA long descriptor and clinical guidance, refer to the current CPT code manual.
What is the Medicare payment for CPT 99359?
The national average Medicare payment for CPT 99359 is approximately $39.08 in a non-facility setting and $32.4 in a facility setting. Actual payment varies by locality based on GPCI adjustments. Total RVU is 1.17 with a conversion factor of $33.4009.
What is the global period for CPT 99359?
CPT 99359 is an add-on code (indicator ZZZ). Its global period matches the base procedure it's billed with. Cannot be billed alone. Must be paired with a primary code per CPT guidelines.
What codes bundle with CPT 99359?
CPT 99359 has NCCI Procedure-to-Procedure edits with 10+ codes including 0362T, 0373T, 0469T. Modifier indicator 0 means the edit cannot be bypassed. Indicator 1 means modifier 59 or X-modifiers may allow separate billing with documentation.
CPT codes and descriptions are copyright of the American Medical Association. RVU values reflect current CMS publications. Actual payment varies by locality. Commercial payer rates vary by contract.
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We audit your last 90 days of claims and surface the revenue leakage: wrong modifiers, missed bundling appeals, ICD-10 specificity gaps. AAPC-certified coders. 2.49% of collections. No setup fees.