Offers for Sale - Nuh Uh
Many businesses (and frighteningly not all) are aware that non-confidential disclosure of an invention before filing a patent application can render it unpatentable. Noting that there are exceptions (such as grace periods in some countries) to this rule, but why limit your potential?
However, few businesses realise that commercial working of an invention before filing can also render it unpatentable. Even if commercial negotiations are in confidence.
Commercial working can come in a number of forms including making money through sale of the product. However, the most insidious version of commercial working that catch you out is an offer for sale.
In commercial law an offer for sale is an offer that is made with pricing and numbers such that the offer can be accepted by the party to whom the offer is presented. The offer does not need to be accepted to be considered commercial working and potentially invalidating patentability.
So file your patent applications before you offer an invention for sale.
As always, make sure that your commercial considerations are aligned with the IP considerations.