The short answer is that there aren’t any
Informal tender rules. Whereas a formal tender will observe certain protocols, an informal tender will not. This means that the buyer is not obliged to follow any particular course of action, allowing much more flexibility. For the seller, however, there will be much less certainty about the course of events. As well as a lack of defined parameters there may be much less certainty about buying criteria.
Sellers who are aware of these aspects can use them in their favour. Not only is the buyer not obliged to follow certain protocols, the seller isn’t either. They may, for example, take the opportunity to develop a relationship with the buyer, something that is definitely unlikely to be part of the formal tender process!
For help with an informal tender and Informal Tender Rules contact me.