I am party to a number of contracts (website terms of service, for example), where a service operator writes the contract, and I agree to the contract by using the service. If the other party wants to amend the contract, they make available to me a new version of the contract, and the new contract is binding when I next use their services.

Intuitively, two should be able to play at this game, no? I can write up my own contract, or an amendment to the existing contract, and give them reasonable notice, and it should become binding on them if they continue to provide services to me when I request them. Under this theory, it's their responsibility to read and understand my contract, and refrain from doing business with me if my terms are not to their liking.

Is this likely to hold up in court? Or, better yet, is it likely to convince the other party to comply with my contract? Or is this sort of agreement-by-performance only binding in certain contexts, or for certain types of services? (For example, is the situation different between a web site that I browse and a service I subscribe to that sends me something in the mail every month in exchange for money?)

If in theory a contract can be amended by giving notice of terms and waiting for the other party to perform, what kind of notice is reasonable to give a large entity like a corporation? Presumably shooting off an e-mail to their automated support system would be insufficient.

  • I can't imagine you writing Amazon and saying that they agree to sell you Prime services for $.50 a year, and they don't respond, that you would be successful in litigating that. Usually this amounts to "if you don't like our terms, feel free not to use our services", and unless you are buying significant resources (think server farm negotiated data rates) it is unlikely you can get them to agree to individual changes.
    – Ron Beyer
    May 16, 2018 at 2:57

1 Answer 1


Offer and Acceptance

For a contract to be a contract there must be an intention on both parties to create legal relations - this is usually considered in terms of an offer and acceptance.

When Website Co makes an offer to the world, you accept it by clicking the ToS acknowledgement and using the service. This is explicit acceptance of the offer.

The ToS contain provisions that Website Co may amended or replace the ToS by giving you notice, when this happens the contract is still in force as the contract contemplattes its own variation: it doesn't need to be varied by another contract. They do allow you to opt out of the contract by no longer using the service but they are not obliged to do so.

The ToS do not contain provisions allowing you to modify them. Therefore when you write to them you are making an offer to vary the contract. They can accept it explicitly or by conduct. They won't accept it explicitly. They aren't engaging in any conduct that is not already subject to the existing contract so they aren't accepting it by conduct.

  • 1
    So presenting terms can't vary an existing contract, since you can't accept by conduct if the conduct is governed by an existing contract. What if I present my terms first, and specify that responding to my web request or cashing my first check constitutes agreement to my terms of service? Then there's no existing contract governing the conduct, so a new contract with my terms would be created, right? And although the other party may later present their own terms, I could persist in any conduct governed by my original contract without agreeing to them.
    – interfect
    May 22, 2018 at 16:45
  • How can your actions constitute their acceptance? Sending them a cheque or a web request is something you do (legally a cheque is equivalent to cash so banking one is not a sign of consent.
    – Dale M
    May 22, 2018 at 21:27
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    The sending of the check or the request, with terms attached, is the offer; the cashing of the check or fulfillment of the web request, by the other party, is the acceptance. Terms on checks in payment of a debt may not create contracts, but unsolicited checks with additional terms are in practice used to make loans to people: deseretnews.com/article/577620/… For a web request it may be impossible to create a contract, because you're just feeding your terms into an automated machine that you know won't read them.
    – interfect
    May 24, 2018 at 21:02
  • @interfect cashing a Chequers is not acceptance of an offer. Any offer. If you cashed the cheque described and refused to pay the loan, they could sue for return of the money on an unjust enrichment basis (and maybe fail because of their culpability) but not under the non existent contract.
    – Dale M
    May 24, 2018 at 21:08
  • 3
    North Carolina has laws specifically regulating loans governed by check-cashing terms: ncleg.net/EnactedLegislation/Statutes/PDF/BySection/Chapter_75/… So "an unsolicited check made out to the recipient that upon cashing, obligates the recipient to repay the amount of the check plus interest and fees" is a thing that can exist in at least one jurisdiction.
    – interfect
    May 24, 2018 at 22:44

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