Complaint letters are usually written in the wrong order, which is the order the events actually happened in. The writer begins at the beginning, builds through the frustration chronologically, and arrives at what they want somewhere near the bottom of page three, by which point the reader has skimmed. Reversing that is most of the technique. A letter that opens with the conclusion and then supports it can be read, understood and acted on in under two minutes, which is roughly the attention any individual complaint is going to receive.
The First Two Sentences Do Most of the Work
Open with what happened and what you want, in that order and in one short paragraph. Something bought on a date failed in a stated way, three attempts to resolve it have not worked, and the request is a refund of a specific amount. The person opening the envelope now knows the entire matter and can decide whether it is theirs to handle before reading anything else, which is exactly the outcome a complaint needs from its first contact.
Include the reference numbers in that opening block, on their own lines above the text if necessary: account number, order number, invoice number, the date of the transaction and any case number from previous contact. A reader who has to search a system to find out who you are will put the letter down and come back to it, and coming back to it is the point at which most complaints quietly stop moving. Everything that lets somebody act immediately belongs at the top.
The Account, Told Once and Without Adjectives
The second paragraph is the factual history, and it should be shorter than feels adequate. Dates, what happened, what was said and by whom, in sequence, with no characterization of anybody's behavior. Unacceptable, appalling and disgraceful all invite the reader to form a view about the writer rather than about the facts, and a flat account of somebody being told three times that a callback was coming is considerably more damning than any adjective applied to it.
Keep it to the events that bear on the request. A letter seeking a refund for a failed appliance does not need the detail about the delivery driver, however annoying that was, because every additional grievance gives an unwilling reader another thing to dispute. One clean line of causation, from what was promised to what was delivered to what was requested and refused, is what a decision maker needs and all they need.
The Request, Which Has to Be a Decision Somebody Can Make
The third paragraph restates the request precisely, with a number attached where money is involved and a description of what would settle the matter where it is not. Repair the unit and extend the warranty by the period it has been unusable. Refund the installation charge of a stated amount. Cancel the contract without the early termination fee applied on a stated date. Anything that requires the reader to work out what would satisfy you will be answered with an apology instead.
Proportion matters as much as precision. A request the reader can approve within their own authority frequently gets approved on the first pass because approving it is faster than escalating it, and a request that obviously exceeds that authority triggers a process instead. If the sum is large, saying what evidence supports the figure keeps it in the territory of a claim rather than a demand.
Choosing Between an Email, a Letter and the Form
The channel matters more than the wording in one specific respect, which is whether it produces a record and reaches somebody with authority. A web form is convenient and generally arrives in the same queue as everything else, which is fine for a routine problem and useless for one that has already been through that queue twice. Email to a named person is faster and creates a timestamped record. A physical letter sent with proof of delivery is slower and carries a weight the other two do not, largely because somebody has to open it and decide what to do with the paper.
The Closing Paragraph and What Goes With the Letter
Finish with a date and a consequence, both stated neutrally. A response within fourteen days is reasonable, and naming what follows if none arrives, a complaint to a named regulator, a filing in small claims court, a dispute with the card issuer, converts the deadline into a real one. Only name a step you are actually prepared to take, because a threat that is not followed through teaches the recipient exactly how much attention future letters need.
Attach copies rather than originals, listed at the bottom so the reader knows what should be there, and keep the total short enough that the whole package can be read at a desk. Send it in a way that produces a record of delivery, since the date of receipt is what the deadline runs from and it is the fact most often disputed later. One page, four paragraphs and a small stack of numbered attachments is not a modest complaint. It is the version that a person with the authority to fix the problem can act on before their next meeting, which is the only test that matters.