What the A, B and C Codes Mean on Australian Patent Publication Numbers

When you look up an Australian patent, you’ll often see a publication number like:

• AU2023123456A

• AU2021123456B2

• AU2021123456C1

These final letters — A, B and C — are not random. They tell you exactly what stage the patent is at and whether it is enforceable.

This system is formally defined by IP Australia’s Patent Document Kinds classification.

A = Published Application: An A‑document is the first publication of a patent application.

According to IP Australia, A‑series codes include:

A1 — Published application (OPI document)

A2 — Amended published application

A8/A9 — Corrected versions of A‑series documents

Key points for business owners:

• The invention is now public

• The patent is not yet granted

• The owner cannot enforce rights

Competitors can review the claims and prepare for what may come next

An A‑document is a public notification, not a legal barrier.

B = Granted Patent

A B‑document means the patent has passed examination and is now legally enforceable.

IP Australia defines B‑series codes as:

• B1/B2 — Accepted standard patents

• B3/B4 — Granted petty/innovation patents

• B8/B9 — Corrected versions of B‑series documents

This is the critical stage for SMEs because:

• The owner can now sue for infringement

• You must assess your freedom to operate

• You may need design‑around strategies

• Investors often require confirmation of grant

If you see a competitor’s patent ending in B, it’s time to pay attention.

C = Corrected or Amended Document

A C‑document is a corrected or amended version of an earlier publication.

IP Australia defines C‑series codes as:

C — Amended after acceptance/grant (pre‑2002 filings)

C1/C4 — Amended after acceptance or certification

C8/C9 — Corrected versions of C‑series documents

A C‑document does not change the patent’s legal status — it simply replaces the earlier version with corrected information.

Why These Codes Matter for Your Business

Understanding these codes helps you:

• avoid infringement

• assess competitor activity

• make informed R&D decisions

• track your own patent’s progress

• communicate clearly with investors and partners

These codes are also used by examiners when categorising prior art documents, as confirmed in IP Australia’s examination manual.

Common Misconceptions

“A patent ending in A is already enforceable.”

No — only B‑documents represent granted rights.

(Confirmed by IP Australia’s distinction between A‑series and B‑series documents.)

“C means the patent has changed.”

Not necessarily — it may simply correct a typo or formatting issue.

(C‑series includes corrected bibliographic data and reprints.)

“If it’s published, I can’t commercialise my idea.”

Not true — only granted patents (B‑series) create enforceable rights.

Need help interpreting a patent?

At Inventiq, we help Australian businesses understand patent documents, assess risk, and protect their freedom to operate.

If you’d like a professional review, get in touch.