Varying: changing the deal without ending it
Business moves. Scope grows, dates slip, prices get renegotiated, and the contract you signed in March is not the arrangement you are running in November. That is normal, and varying a contract is the ordinary way to keep the paperwork honest.
The catch is that a variation is not a memo. It is a new agreement, and it needs the same thing a new agreement needs: consideration. Each side has to be giving something. Where the change is genuinely two-way - you extend the deadline, they drop the price - that is easy. Where it is one-way, it is not, and that is where variations quietly fail.
The classic example is the customer who agrees to accept less than the full debt. If nothing is given in return, that promise is often unenforceable, and the balance can be pursued later despite everyone shaking hands on it. If a variation is genuinely one-sided, the clean answer is to execute it as a deed, which does not need consideration at all.
The no-oral-modification trap
Most commercial contracts contain a clause saying no variation is effective unless it is in writing and signed by both parties. It sits at the back with the boilerplate and everybody ignores it.
They should not. The Supreme Court settled this in 2018: those clauses work. If your contract says variations must be written and signed, then an oral variation - agreed on a call, confirmed by a handshake, acted on by both sides for months - is not a variation. The original terms still govern.
That is a hard rule and it produces uncomfortable results. Two parties can genuinely agree something, both perform on that basis, and one of them can later insist on the original terms because nobody wrote the change down. There are narrow escape routes where one party has relied on the change to their detriment, but they are narrow, and you do not want to be arguing about them.
The boilerplate at the back is not decoration. It is the clause that decides whether the deal you are actually running is the deal you can actually enforce.
The practical habit is dull and free: when you agree a change, write it down, say it is a variation to the contract of whatever date, and get it signed by someone with authority on both sides. Ten minutes, and it removes an entire category of argument.
Terminating: two doors, and you should say which
There are two entirely separate ways a contract ends early, and conflating them is one of the more expensive habits in commercial life.
- The contract's own termination clause. A contractual right you negotiated - for convenience on notice, on insolvency, on a material breach not remedied within a stated period. Its scope is whatever the clause says, no more and no less.
- The common law right. The right that arises when the other side commits a repudiatory breach - one serious enough to deprive you of substantially the whole benefit of the deal. It exists whether or not the contract mentions it.
They are not interchangeable. The clause may require notice and a cure period the common law does not. The common law needs a breach far more serious than "material" usually means. And the damages can differ: terminate under a clause and you may only recover losses up to termination, where accepting a repudiation can let you claim for the loss of the whole bargain.
Which is why a well-drafted termination letter usually relies on the clause and the common law right in the alternative, and expressly reserves all other rights. It costs nothing to do and it means one route failing does not take the whole termination down with it.
The letter is the whole case
Almost all the termination disputes that should never have happened come down to mechanics rather than merits. The right existed. It was exercised badly.
So read the notices clause before you write anything, and do exactly what it says. Who has to give the notice, and to whom. What form it must take - and whether email counts, because plenty of contracts still say it does not. Which address it goes to, which is frequently the registered office and not the person you have been emailing for two years. How much notice, counted in business days or calendar days. When it is deemed received, which is often two days after posting whatever actually happened.
Then say plainly what you are doing, on what ground, and from when. A termination letter that is vague about its own basis invites the argument it was trying to end.
Frequently asked questions
What is a variation of a contract?
A variation is an agreement to change the terms of an existing contract while keeping it alive. Because it is itself an agreement, it normally needs consideration - each side giving something - or it must be executed as a deed. Many contracts also require variations to be in writing and signed, and that requirement is enforceable.
Can a contract be varied orally?
Only if the contract does not prohibit it. Where there is a clause requiring variations to be in writing and signed, the Supreme Court confirmed in 2018 that an oral variation is ineffective - even where both parties clearly agreed it and acted on it. Without such a clause an oral variation can be valid, but proving its terms later is its own problem.
What is the difference between terminating under a clause and at common law?
A termination clause is a right you negotiated, and it does exactly what its wording allows - often requiring notice and a chance to remedy. The common law right arises independently when the other party commits a repudiatory breach. The grounds differ, the procedure differs, and the damages can differ, so it matters which one you are relying on.
What should a termination letter say?
Plainly: that you are terminating, the ground you rely on, the clause or right you are exercising, and the date it takes effect. It should follow the contract's notice provisions exactly - correct recipient, correct address, correct method, correct notice period - and should reserve your other rights. Where more than one route is available, careful letters rely on them in the alternative.
What happens if I terminate a contract wrongly?
Refusing to perform a contract that is still alive is a repudiatory breach by you. The other party can accept it, treat the contract as at an end and claim their losses. That is why the ground and the mechanics both need checking before the letter goes out, not after the response arrives.
Ten minutes now, or a year of it later
Whether a change was validly agreed and whether a termination actually worked are both answerable quickly, in advance, by someone who has read the contract. Silva does exactly that - the variation drafted properly, or the letter checked before it goes.