Most rejected cover letters fail for the same reason: they are the CV again, only in paragraphs. The candidate takes the work history, adds connective tissue like "I then joined" and "where I was responsible for", and sends a page that tells the recruiter nothing new. If the two documents say the same thing, one of them is dead weight.
They are not two versions of the same story. They do different jobs, get read by different people, at different moments, for different reasons.
The CV is a record. The letter is an argument.
A CV exists to be scanned and verified. It is a factual inventory: what you did, where, when, and with what result. It gets parsed by software, skimmed by a recruiter in well under a minute, and pulled back up later as a reference during interviews and salary discussions. Nothing in it should require the reader to accept your interpretation of events. Dates, titles, tools, numbers.
A cover letter exists to make a case for one specific role. It answers the question a CV cannot: why this job, why this company, why now, and why the gaps between your history and their requirements do not matter. It is written in the first person, it has a point of view, and it is only useful if someone actually reads prose.
That difference drives everything else.
Side by side
| | CV | Cover letter |
|---|---|---|
| Core job | Evidence of what you have done | Argument for why you fit this role |
| Length | 1-2 pages, dense | 250-350 words, one screen |
| Voice | Impersonal, mostly verb-led fragments | First person, full sentences |
| Tone | Neutral and factual | Warm but professional, some personality |
| Structure | Fixed sections, reverse chronological | Free-form, 3-4 short paragraphs |
| Tailoring per application | Light: reorder, swap keywords | Heavy: mostly rewritten each time |
| First reader | An ATS, then a recruiter skim | A human, if anyone |
| Reused later | Yes, in interviews and internal notes | Rarely, often never opened |
The tailoring row is where people misallocate effort. Rewriting your CV from scratch for every application is mostly wasted work. Rewriting the letter is the whole point of having one.
What belongs where
Things that belong in the letter and almost never in the CV:
- Motivation. Why this company rather than the four others hiring for the same title.
- Explaining a gap. A career break, a redundancy, a health period, a year abroad. The CV shows the dates honestly and moves on; the letter gives them a sentence of context if it helps.
- A career change. The CV cannot argue that six years in hospitality prepared you for account management. A letter can.
- Relocation. You live in Manchester, the job is in Bristol, and you are already moving. Say it, or the recruiter will assume you are not.
- Availability and notice period, when it is unusual or worth flagging early.
- Salary context, only if the posting asked for expectations.
Things that belong in the CV and should not be re-listed in the letter:
- Full employment history
- Every tool and technology you have touched
- Education, certifications, languages
- Contact details beyond a signature line
The mistake that kills most letters
Duplication. If a recruiter can read your letter and learn nothing that was not already on page one of the CV, the letter has cost them thirty seconds and given them zero. Worse, it makes the application feel automated even when it is not.
The fix is to decide what the letter is for before writing a word. Pick one thing: the reason you want this role, the one experience that maps directly onto their hardest requirement, or the objection you know they will raise. Build the letter around that, and let the CV carry the rest.
How the two should reference each other
The letter should point at the CV without reciting it. "The migration project on my CV was the closest thing I have done to what you describe in point three of the posting, and here is what it actually involved" is a good move. It sends the reader to a specific line and adds the context that a bullet point cannot hold.
Going the other way, your CV should be strong enough to stand alone. Assume the letter will not be read. Many recruiters open the CV, decide, and never scroll to the attachment.
When you can skip it
Norms vary, and it is worth knowing which market you are in.
In the UK and US, cover letters are increasingly optional. If the application form marks it optional and you have nothing specific to say, a generic letter is worse than none. Send one when you are changing sector, when the posting explicitly asks, when you have a referral or a gap to explain, or when the employer is small enough that a human reads everything.
Some applications actively discourage them. Big graduate schemes and structured application forms often replace the letter with targeted questions, which serve the same purpose in a format they can score consistently. Answer those properly rather than pasting a letter into a text box.
When the letter is just an email
Applying by email changes the shape but not the function. The email body becomes the letter, so it needs to be shorter, roughly 120-180 words, with the argument in the first two sentences because half of it will be read on a phone. Use a subject line that names the role and any reference number. Attach the CV as a PDF with a filename that includes your name. Do not write a two-line email saying "please find my CV attached" and then attach a separate letter file; nobody opens the second attachment.
Before your next application, run one check: read your letter and delete every sentence that restates something already on your CV. If what is left is three sentences, that is your real letter, and it is more useful than the page you started with.