An association within the meaning of the Basic Law is a permanent voluntary link that should not be limited to a business. In addition, each association must consider itself a representative of workers or employers and work expressly towards collective agreements. Once an offer is made, the general rule is that the offeror must notify his agreement in order to have a binding agreement.  The acceptance notification must indeed reach a point where the supplier can reasonably assume that it is willing to know, for example by not putting enough ink in its fax machine for a message to arrive in office hours.  This applies to all methods of communication, whether oral, telephone, telex, fax or e-mail, with the exception of the mail. Acceptance by letter is made when the letter is placed in the mailbox. The postal exception is a product of history and does not exist in most countries.  It exists only in English law as long as it is useful to use mail for a reply (for example.B. not as a response to an e-mail), and its operation would not cause obvious inconvenience and nonsense (for example.B. the letter is lost).  In all cases, the parties to the negotiations are able to establish a mandatory method of adoption.  It is not possible for a bidder to impose an obligation on the bidder to refuse the offer without its consent.
 However, it is clear that people can accept by silence, first by demonstrating by their behavior that they accept. In Brogden/Metropolitan Railway Company, the Metropolitan Railway Company had never returned a letter from Mr. Brogden formalizing a long-term supply agreement for Mr. Brogdeniser`s coal, but behaved for two years as if it were in force and Mr. Brogden was bound. Second, the supplier may waive the need for express or implied notification of acceptance, as in Carlill v Carbolic Smoke Ball Company.  Here, a charlatan promoted his «smokeball» and explained that if a customer found out that he would not cure her of the flu after using it three times a day for three weeks, he would receive $100. After the announcement was serious enough to be an offer, not only to deal with the brothel or an invitation, the Court of Appeal held the agreed party only necessary to use the smoke balloon, as prescribed, to get the $100. Although the general rule was to require notification of acceptance, the information had implicitly waived that Ms. Carlill or anyone else had to first signal her acceptance.