What are the core questions?
The USPTO's MPEP 2152.02(d) explains that an on-sale issue involves a commercial sale or offer for sale and an invention ready for patenting. For applications governed by AIA section 102, the statutory text also requires attention to effective filing dates and the exceptions in section 102(b). Do not assume every disclosure receives a one-year grace period.
What evidence should I collect?
Preserve dated offers, purchase orders, contracts, drawings, prototypes, and records showing what the parties agreed to supply. Identify which claim features were present and when. Have counsel examine confidentiality, transaction terms, and the governing law rather than deciding the issue from a document's label.
Can any prior-sale evidence be used in any Patent Office challenge?
No. Section 311(b) limits inter partes review grounds to sections 102 and 103 based on patents or printed publications. Section 302 similarly frames reexamination requests around prior art cited under section 301. A witness account or sales transaction is not automatically an eligible IPR ground merely because it may matter in court. Match the evidence to the chosen procedure.