When cover letters genuinely matter
Small and medium-sized businesses
At smaller companies, the person hiring is often the person you would work for. They frequently do read cover letters, partly because the volume is lower and partly because culture fit matters more at that scale. A thoughtful cover letter at a 30-person company can be the thing that gets you an interview over a stronger CV from someone who seemed less interested.
Career changes
If your CV does not immediately explain why you are applying for this type of role, a cover letter gives you the space to make that case. A former teacher applying for L&D roles, or an operations manager pivoting into project management, needs to tell that story somewhere. The cover letter is the right place.
Roles that specifically require one
If the job posting says "please include a cover letter" and you do not, you have already made a mistake. Some employers use the cover letter as a basic test of whether candidates follow instructions.
Speculative applications
If you are contacting a company that has not advertised a specific role, a cover letter is essential. There is no job description for your CV to respond to, so you need to explain who you are and what you are offering clearly.
When cover letters probably do not matter
At large companies with high application volumes, most cover letters are not read unless a CV has already been shortlisted. At that point, the recruiter already has an opinion about your candidacy from your CV alone. A mediocre cover letter here does limited damage; a great one does limited extra benefit.
The safest assumption is that your cover letter might be read. Write one that is worth reading.
What a good cover letter actually looks like
Three short paragraphs. No more than 300 words. Written specifically for the role and company.
Paragraph 1: Why this role, at this company
This is the most important paragraph and the one most people write worst. "I am writing to apply for the position of Marketing Manager as advertised on LinkedIn" tells the reader nothing they do not already know. Instead, say something specific: why this company, why this role, why now. One sentence of genuine interest is worth more than three sentences of generic enthusiasm.
Paragraph 2: What you bring
Pick the one or two most relevant things from your experience and connect them directly to what the role requires. Do not summarise your entire CV. If the role asks for someone who can manage agency relationships and you have done that for three years, say so and say what the result was.
Paragraph 3: A brief close
Thank them for their time, confirm your interest and note that you have included your CV. No need for elaborate sign-offs.
The opening line problem
The single most common mistake in cover letters is the opening line. "I am writing to apply for..." "I was excited to see your listing for..." "As a passionate and driven professional..." These openers are so common that they read as invisible. Start with something specific and interesting instead.
If you managed a transition that saved your last employer significant time, open with that. If there is something specific about this company's product or mission that genuinely connects to your experience, open with that. Make the recruiter want to read sentence two.
Length and format
One page maximum. 250 to 350 words is ideal. Use the same font and formatting as your CV so the two documents look like they belong together. Address it to a named person if at all possible; "Dear Hiring Manager" is acceptable but "Dear [Name]" is better.
One final check: Read your cover letter and ask whether it could have been written by any candidate for any similar role at any company. If yes, make it more specific. The more clearly it responds to this role, at this company, the more likely it is to work.