You can put together a decent CV in a language you only half control. Job titles, dates, tool names, a bullet that starts with "Led" and ends with a number: the format carries you. A cover letter offers no such shelter. It is continuous prose, it has to persuade, and every sentence tells the reader something about your relationship with their language whether you want it to or not.
That is the whole problem in one line. A CV is a document you fill in. A cover letter is a document you write.
Why the letter exposes what the CV hides
A CV lives in fragments. Nobody expects a full sentence, so nobody judges your syntax. Recruiters skim it for evidence, not style, and a slightly odd phrase in a bullet reads as compression rather than error.
The letter reverses that. You need subordinate clauses, connectors between ideas, a way to say "I want this job" that sounds confident rather than desperate, and a way to say "I am aware I lack X" that sounds honest rather than apologetic. Those are the moves a second language makes hardest. Tone lives in tiny choices: whether you say "I would be glad to" or "I want", whether you use the conditional, whether your closing line asks or assumes.
There is a second, quieter problem. A letter that reads as machine-produced does not just look linguistically weak. It suggests the candidate did not spend much time on the application, which is a judgement about effort rather than grammar. That is the more damaging read.
Greetings and sign-offs are a register test
The opening line is the first thing the reader processes and the easiest thing to get subtly wrong.
In English-speaking markets, "Dear Hiring Manager" is safe when you have no name and "Dear Ms Okafor" is better when you do. "To Whom It May Concern" survives in templates but reads as stiff to most readers now. "Hi there" works for a startup and jars in a law firm. British English sits a notch more formal than American English for the same role, and the difference shows most in the sign-off: "Kind regards" is unremarkable in London and slightly ornate in Chicago, where "Best regards" does the same work.
French letters run formal by default, and the closing formula is longer than anything an English speaker would write voluntarily. A learner who ends a French letter with the direct translation of "Best regards" has signalled foreignness in four words. The safer path is to lift a standard closing formula intact rather than to invent one.
The same language behaves differently across borders too. A letter for a Madrid employer and one for a Mexico City employer are both in Spanish, and the second will typically be warmer and less rigid in its address forms. English in Singapore is not English in Sydney. If you can read letters or job ads written by people inside the target market, do it: register is absorbed far better than it is taught.
One practical rule that costs nothing. Match the formality of the job ad itself. If the ad addresses you informally and uses contractions, a rigid letter will feel out of place. If the ad is written in careful institutional prose, meet it there.
The tells of a translated letter
Readers rarely identify machine translation by pointing at a specific error. They just feel that something is off. Here is what they are actually reacting to.
Sentences that are too long. Every language has a comfortable clause length, and translation tools preserve the source structure rather than rebuilding it. A French or Spanish sentence carried into English keeps its subordinate stack and arrives at forty-five words, which no native English business writer would produce on purpose.
Connector overuse. "Moreover", "furthermore", "indeed", "thus", "in addition". Romance-language writing uses explicit connectors far more freely than English does, so a translated letter ends up scaffolded like an essay. English prose links ideas by order and by short sentences, and drops the connective tissue.
Idioms translated word for word. These make readers wince. If a phrase feels colourful in your head, it is probably an idiom, and idioms almost never survive the crossing. Say the plain thing instead.
Calques. Structures borrowed intact from your own language. A Spanish speaker writing English may produce "I have 5 experience in" or "I count with experience in" because the underlying verb pattern is different. A French speaker may write "I dispose of a solid background". These are grammatically legible and immediately foreign.
Over-formal vocabulary. The most common tell of all, because learners are taught the formal register first and translation engines default upward. Words like "endeavour", "utilise", "aforementioned" and "herewith" do not make a letter sound professional in English. They make it sound like it was written in 1955, or by software.
False friends. The word that looks identical and means something else. "Actually" is not "actuellement" or "actualmente". "Assist" is not "asistir a". "Sensible" is not "sensible". These slip past both the writer and the spellchecker.
Write shorter on purpose
Here is the strategy that changes the most for the least effort: deliberately lower your ambition, sentence by sentence.
A simple correct sentence reads as competent. A complex broken one reads as struggling. Nobody was ever rejected for writing clearly. If you catch yourself building a sentence with three clauses and a relative pronoun you are unsure about, cut it in two and move on. The result is not childish. It is closer to how good business writing works in English anyway.
This applies to vocabulary too. Use the word you actually own. If you are not certain how "leverage" behaves as a verb, write "use". Reaching for an impressive word you half know is how you produce a sentence that is wrong in a way you cannot see.
Length follows the same logic. A tight three-paragraph letter in a second language beats a full page that spends its final third repeating itself. You have less room for error, so take less room.
What to say about your language level
The instinct is to apologise in the first paragraph. Do not. An apology at the top reframes the entire letter as an excuse, and it also draws attention to something the reader may not have noticed.
Decide first whether the subject is even relevant. If the letter is in the working language of the role and reads well, say nothing. Your competence is on the page. If the role requires a language you are still building, or there is an obvious mismatch between your background and the language of the application, one factual line does the job, placed in the body rather than the opening.
Something like: "I work in English daily with our engineering team in Dublin and I am currently at B2 in Dutch, with lessons twice a week." That is a statement of fact and a statement of trajectory. It is not an apology, it contains no hedging, and it gives the recruiter something concrete instead of a vague reassurance.
Two things to avoid. Do not claim fluency you cannot sustain in an interview, because the interview will happen in that language and the gap will be visible within a minute. And do not use phrases like "please excuse my mistakes" or "I hope my level is sufficient". They invite the reader to start hunting for errors.
When the ad and the workplace speak different languages
This trips people up constantly. A Berlin company posts in English because it recruits internationally, but the team runs its stand-ups in German. A Barcelona employer advertises in Catalan and works in Spanish with clients across Latin America. Which language do you write in?
The default is the language of the advertisement. Someone chose it, and answering in the language you were addressed in is the safe read.
The useful exception is when you see clear evidence of the internal working language and you are strong in it. The move then is not to switch, it is to demonstrate. Write in the language of the ad and add one concrete detail proving you also operate in the other one: a project you delivered in it, a team you worked with, a certification with a date. That beats a whole letter in a language nobody asked you for.
If the posting is genuinely ambiguous and the company is local, the local language signals commitment. If your level there will not survive a full page, write in the language you control. A confident letter in the wrong language beats a stumbling one in the right language more often than people expect.
Four rewrites
Before: "I take the liberty of addressing you in order to submit my candidature for the aforementioned position which you have published on your website."
After: "I am applying for the Data Analyst role you posted last week."
The original is a translated formal French opening. It uses twenty-five words to say nothing about the candidate and delays the only useful information to the end.
Before: "Thanks to my rigour and my great capacity of adaptation, I am persuaded that I could bring a real added value to your dynamic company."
After: "In my last role I took over a reporting process from a colleague who left, learned the system in three weeks, and cut the monthly close from six days to four."
The original is translated self-description with nothing checkable in it. "Persuaded" is a calque, and "dynamic company" survives only in translated letters.
Before: "Moreover, it is important to underline that I dispose of a solid experience in the domain of the digital marketing, and furthermore I master perfectly the tools of analysis."
After: "I have spent four seasons in digital marketing and I work daily in Google Analytics and Looker Studio."
Connector overuse, a calque on "dispose of", the article before an abstract noun, and "master perfectly", which is a direct import that English does not use.
Before: "I remain at your entire disposition for any complementary information and I beg you to accept, Madam, the expression of my distinguished salutations."
After: "I am happy to provide any further detail. Best regards, Priya Raman."
The closing formula is correct in French and unusable in English. Lift the target language's conventions, not your own.
A proofreading pass that catches different things at each stage
Each of these steps finds a category of error the others miss, so the order matters.
Stage one: a translation tool, used backwards. Write the letter in the target language, then run it back into your own. If the reverse translation drifts from what you meant, the target-language sentence is ambiguous. This catches structure, not word choice.
Stage two: read it aloud. This is the step people skip and the one that pays. Reading aloud exposes rhythm, so it catches sentences that are too long to breathe through, repeated openings, and clumsy transitions. If you run out of air in a sentence, the sentence is too long. If you stumble on a word, so will the reader.
Stage three: a native reviewer. No tool substitutes for this, and the ask should be specific. Do not say "check my English". Say: "Does this sound like a person or like a translation? Is the tone too formal for this company?" A native speaker fixes grammar automatically but only comments on register if you ask.
Stage four: leave it overnight. You catch your own calques far better with a day's distance, because you stop hearing your intended meaning and start reading what is actually there.
With no native reviewer available, the read-aloud pass plus a full day of distance recovers a surprising amount of what stage three would have caught.
Before you send
Read the letter once against each of these.
The greeting matches the market and the company's own tone. Nothing is longer than about twenty-five words. There are at most two formal connectors in the whole letter. Every idiom has been replaced with a plain statement. No word appears that you could not use confidently in conversation. The closing formula is one you copied from the target language, not one you translated. There is no apology about your level anywhere. At least one concrete, checkable detail sits in the second paragraph. The hiring manager's name is spelled correctly, along with the company's. And the whole thing fits on well under a page.
A letter that follows those rules will not read as ambitious. It will read as clear, which is the thing you were actually being judged on.