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Error code

MO — Maximum OCT (Optical Coherence Tomography) services reached

OCT limit reached

The patient has reached the maximum optical coherence tomography (OCT) services for the period, such as 4 per 12 months.

What to do: Count OCT services paid in the period; if the limit is reached and neovascularization is actively managed, G822 may apply.

Code
MO
Description
Maximum OCT (Optical Coherence Tomography) services reached

Explanation

Updated October 26, 2026

MO means the patient has reached the maximum OCT (optical coherence tomography) services for the period. Check the OCT limits.

What it means

MO means the maximum number of Optical Coherence Tomography (OCT) services has been reached.

Any combination of G818, G820 or G821 is limited to 4 per patient per 12 months, and G820 to 2. G822 is paid only once that limit is reached, up to 8 per 12 months and 16 per 24 months. G823 (under 18) is limited to 12 per 12 months. Only one OCT code is paid per patient per day (Schedule J93 to J94).

Common causes

  • A fifth G818/G820/G821 service in 12 months
  • G822 billed past its own limit
  • More than one OCT code on the same day

How to fix it

  1. Count OCT services paid for the patient in the limit period.
  2. If the G818/G820/G821 limit is reached and the patient is in active management for neovascularization, G822 may apply (Schedule J93).
  3. If you believe the decision is wrong, send a Remittance Advice Inquiry (RAI) through eSubmit, or on form 0918-84, within 7 months of the RA date, with supporting details.

Don't resubmit if

  • The OCT limit for that code was reached.
  • The line is already on your RA. Question it with an RAI, not a new claim.

How APEX handles it

APEX reads your error reports and remittance advice from MCEDT and lists claims rejected with this code in its Correction Centre for you to correct and resubmit. See how APEX works · Pricing

Related codes: MY, M4

Sources