A and B agree a contract.  At some later date A wishes to modify the
contract.  What is the principle called that A aren't allowed to modify the
contract unilaterally without B's agreement?  Is there a well-known case at
which this precedent was set?

A can inform B of the new terms and B is deemed to have accepted the
amendment if they do not object within a reasonable time.  A may explicitly
specify a time period for this.  If a time period is defined, is it
necessary to negotiate a new contract within this time or simply for B to
inform A that they object (and thus is it possible to 'stop the clock' such
that the amended contract will not apply at the expiration of the given
period, while new terms are negotiated)?

If B objects to the amendment, can they still hold A to the original
contract?  Or, if the modification is to B's detriment, can B insist on
termination of the contract with no penalty for early termination?

If A is a business and B is a consumer, does this make any difference?

Thanks
Theo

On Oct 4, 3:30 pm, Theo Markettos <theom+n...@chiark.greenend.org.uk>
wrote:
> A and B agree a contract.  At some later date A wishes to modify the
> contract.  What is the principle called that A aren't allowed to modify the
> contract unilaterally without B's agreement?
I don't know if there is a name - the concept is pretty fundamental to
the whole of contract law!

> Is there a well-known case at
> which this precedent was set?

Pass (I wouldn't be surprised if it is just part of common law).

> A can inform B of the new terms and B is deemed to have accepted the
> amendment if they do not object within a reasonable time.
Ish.  If A is supplying (say) a weekly delivery of eggs, and says "the
price has now gone up", and B continues to accept the deliverys, then
B is deemed to have accepted the ammendment.  If on the other hand, A
is supplying (say) a new steel framework for a house, and says "the
price has now gone up", they really need to get B to formally agree
the increase before delivery (otherwise B can probably turn round and
say "no, I don't accept the change in price" - at which point A is
stuffed.)

> A may explicitly specify a time period for this.
They may; it doesn't mean the court will agree with them.

> If a time period is defined, is it necessary to negotiate a new contract
> within this time
No.  B says "I object to the new terms", and the contract continues
unaltered.

> or simply for B to
> inform A that they object (and thus is it possible to 'stop the clock' such
> that the amended contract will not apply at the expiration of the given
> period, while new terms are negotiated)?

> If B objects to the amendment, can they still hold A to the original
> contract?
Yes.  (But note, this is the /original/ contract, so an employer can't
just say "I'm cutting holiday by two days next year", but the employee
can't require them to keep holiday the same /and/ give an annual
inflation salary increase.)

> Or, if the modification is to B's detriment, can B insist on
> termination of the contract with no penalty for early termination?
No.  (But A may prefer that to being held to the original contract.)

> If A is a business and B is a consumer, does this make any difference?

Possibly.  In particular, it may affect whether terms in the original
contract that purport to allow A to unilaterally change the price etc,
are excluded because they are "unfair".

Martin Bonner  wrote:
> On Oct 4, 3:30 pm, Theo Markettos <theom+n...@chiark.greenend.org.uk>
> wrote:
> > A and B agree a contract.  At some later date A wishes to modify the
> > contract.  What is the principle called that A aren't allowed to modify
> > the contract unilaterally without B's agreement?
> I don't know if there is a name - the concept is pretty fundamental to
> the whole of contract law!

Thanks, your answers are most useful.

> > Is there a well-known case at
> > which this precedent was set?
> 
> Pass (I wouldn't be surprised if it is just part of common law).

Indeed, but there seem to be some cases establishing fairly basic tenets of
contract law (eg the Carbolic Smoke Ball case).

My copy of Nutshells is elsewhere, and it's the sort of thing that might be
in it.  I think I shall have to take myself to the library and have a
look...

Theo

Theo Markettos <theom+news@chiark.greenend.org.uk> wrote:
> Indeed, but there seem to be some cases establishing fairly basic tenets of
> contract law (eg the Carbolic Smoke Ball case).
> 
> My copy of Nutshells is elsewhere, and it's the sort of thing that might be
> in it.  I think I shall have to take myself to the library and have a
> look...

Just for the interest of anyone who might be listening, I couldn't find a
precise reference but the case I found that best fit was:

British Movietonenews Ltd v London and District Cinemas (1952) AC166

which basically holds that a change in circumstances which makes the
contract impracticable for one party will not frustrate the contract.

("Frustration" being defined as events beyond each parties control which
makes the contract impossible to fulfill: eg in Taylor v Caldwell 1863)

Theo