POS 81 — Independent Laboratory: Place of Service Code Explained

POS 81: What It Identifies

POS 81 identifies services performed by an independent laboratory — a freestanding, certified lab that is not part of a physician office or hospital (think Quest, Labcorp, and regional independents). It tells the payer the testing happened at a facility whose entire business is laboratory medicine, which drives both the fee schedule applied and the billing rules around who may bill for what.

The confusion around POS 81 is rarely about the lab's own claims — it's about physician offices handling send-out specimens. When your office draws blood but ships the specimen to an independent lab, who bills the test, at which POS, and whether your office can bill anything at all depends on payer rules — and Medicare's anti-markup and reference-lab rules are strict.

Use POS 81 For

Tests performed at a freestanding, independent clinical laboratory
Reference-lab claims billed by the performing independent lab itself
Pass-through billing situations where payer rules permit — reported with the performing lab's location

Don't Use It For

Tests your office performs in-house with its own CLIA certificate — that's POS 11
Hospital lab work — POS 22 (outpatient) or 21 (inpatient)
The specimen-collection fee for an office draw — the venipuncture is billed where it happened (POS 11)

How POS 81 Affects Payment

Clinical lab tests pay under the Clinical Laboratory Fee Schedule rather than the physician fee schedule, so the facility/non-facility distinction matters less than who is allowed to bill. Medicare's rule of thumb: the entity that performs the test bills for it. A physician office billing Medicare for a test an independent lab performed runs into reference-lab restrictions and anti-markup rules — the office generally can't profit on purchased tests, and in most cases the lab should bill Medicare directly. Commercial payers vary: some permit pass-through billing with correct POS and performing-lab identifiers on the claim; others contractually require direct lab billing. Getting this wrong produces refunds, and in Medicare's case, compliance exposure.

Common POS 81 Billing Errors

Office bills a send-out test at POS 11 as if performed in-house — misrepresents the place of service
Marking up purchased tests to Medicare — anti-markup violations are a classic audit finding
Missing performing-lab CLIA/NPI on pass-through claims — instant rejections or CO-16 denials
Billing the draw fee at POS 81 — the venipuncture happened in your office, not at the lab

Related POS Codes

POS 11 — Office POS 22 — On-campus outpatient POS 49 — Independent Clinic

← Back to the full POS code reference

Reviewed by Hassan Raza Awan, Founder — 4+ years of hands-on U.S. medical billing experience. General billing information — verify against current CMS guidance and your payer contracts.

Frequently Asked Questions

Our office draws blood but the lab runs the test — who bills what?

Your office bills the venipuncture/collection at POS 11. The test itself is generally billed by the performing lab at POS 81 — especially for Medicare, where reference-lab rules usually require the lab to bill directly.

Can we bill Medicare for tests we send to Quest or Labcorp?

Generally no — Medicare expects the performing laboratory to bill. Limited reference-lab exceptions exist, and anti-markup rules prevent profiting on purchased tests. When in doubt, let the lab bill.

What's the difference between POS 81 and POS 11 for labs?

POS 11 is for tests your office performs itself under its own CLIA certificate. POS 81 is for tests performed at a freestanding independent laboratory. The POS should reflect where the testing actually happened.

Why did our lab claim deny for a missing CLIA number?

Lab claims must carry the CLIA certification of the performing site; pass-through claims also need the performing lab identified. Missing identifiers produce rejections or CO-16 denials — add the CLIA/NPI and resubmit.

POS 81: Independent Laboratory