Modifier 90: Reference to Outside Laboratory

Modifier 90 is to be used when the billing laboratory refers a specimen to another laboratory for testing. In these cases, the billing laboratory is titled the “referring laboratory” while the laboratory that actually performed the test is the “reference laboratory.”

• Only independent billing clinical laboratories (specialty 69) can bill with the 90 modifier. Sometimes a clinical diagnostic independent laboratory, POS 81, refers a specimen to another laboratory for testing, where a modifier 90 is appended.
  • The billing entity must be designated as a specialty 69 in their provider enrollment record within the PECOS.
• Must append modifier 90 to referred laboratory test code
  • Item 20 mark "Yes" = outside laboratory
  • Purchase price must be reflected under charges
  • Complete item 32 with NPI, name and address where test was performed
• Appropriate modifier 90 claims include two different CLIA numbers on electronic claims
  • Reflect billing provider information
  • Laboratory where services were performed (reference laboratory)
• Electronically bill claims with/without modifier 90 and without modifier 90 separately electronically on the same claim
• If no purchased services, leave item 20 blank
• When the laboratory submits claims, services both performed and referred may be billed on the same electronic claim. Regardless, of the services performed, whenever the 90 modifier is billed on a claim, the following information must be included.

Related Content

• CMS IOM Publication 100-04, Medicare Claims Processing Manual, Chapter 16, Section 40
• CMS IOM Publication 100-04, Medicare Claims Processing Manual, Chapter 1, Section 30.2.9

Revised 10/16/2024