Job-application letters (or cover or covering letters, as they're variously termed) may seem like mere formalities. But if you plan to apply for a science-related position, particularly in the academic, non-profit and industrial sectors, you need to write a spectacular one.

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The document remains your first and best opportunity to act as both agent and salesperson for yourself: if it's done properly, only this component of your entire application package can simultaneously act as introduction, first-stage filter and cogent, compelling argument for your candidacy. Not until the interview — if you get one — will you have another chance to show why you are the best choice for the job.

Researcher applicants who want their cover letter to sparkle need to craft a document that's customized to the position. The letter should concisely explain how your competencies fit the criteria specific to the job, convey your excitement about the position and reveal some of your personality. It should also avoid hyperbole, typographical and other errors and exact duplication of points on your CV or résumé.

Some employers — particularly government agencies and organizations with a specialized online-only application process — do not welcome or use cover letters. But aside from these exceptions, it's best, hirers say, to include a letter, unless a job advert specifically bans it. The document remains an integral part of the recruitment process in industry and academia and for many non-profit organizations.

Why is it so important? Without one, say hiring managers, it can be tricky to identify the best candidates through their CVs and other application materials alone. These often start to sound drearily similar, says Karen Noble, head of research training and fellowships at Cancer Research UK (CRUK) in London, who frequently reviews applications for jobs in grant management or research administration. “Most people have done a PhD, they may have done a postdoc and they are now looking to be involved in administration,” she says. “I want to see why they want to join the organization, and why this job.” She says that an applicant's cover letter to CRUK should make it clear that the candidate has carefully studied the job description, and it should provide specific examples of how their skill set and experience meet the position's requirements.

No robots

If someone is unable to express him- or herself without errors, that is an immediate reject.

Hirers also stress that it is crucial to convey in your application letter that you've learnt as much as possible about the organization and specific job for which you're applying, and that you're not sending a generic submission. What a hiring manager at one company or organization may find powerful and persuasive in a cover letter may be viewed by their counterpart at another organization as irrelevant.

It's also important to spell out exactly how your abilities and interests align with the position, says Aaron Genest, who recruits candidates as part of his job with software firm Solido Design Automation in Saskatchewan, Canada. Because it's rare that an applicant's background exactly matches all of the criteria that hirers seek, it can help to make it clear in your letter that you are willing to do what is necessary to learn the specific skills that the hiring organization needs, such as by taking a course.

When all else is equal — background, education, skills, talents and abilities — getting the job is often down to your personality and how well you might fit in with the team. Outside an in-person interview, only your cover letter can offer a glimpse of your persona and disposition. Kevin Wang, a recruiter at biotech firm Stemcell Technologies in Vancouver, Canada, says that an applicant's 'personal brand', or individuality, is best conveyed in story form in the letter. You might, he suggests, write briefly about a time when you demonstrated your excellence at teamwork or problem solving, or explain in a concise way why you want the job. If you can link a personal interest to the position in some way, you should do so. Wang, who takes part in triathlons, says that if he were writing a cover letter for himself, he would probably include how triathlon training has taught him to be resilient and tenacious in the face of challenges.

Similarly, if you're enthusiastic and excited about the potential job, you should judiciously express that emotion. Cover letters often say things such as “I look forward to working with X”, but you could express this more enthusiastically and with a bit more animation, says Iain Stenhouse, senior science director at the Biodiversity Research Institute in Portland, Maine. Cover letters that are vibrant and creative (but not outlandish) spur him to spend more time on the applicant's CV, he says. “They're where a candidate can really separate themselves from the pack.”

Investigate options

boxed-textThe importance of a cover letter may vary depending on whether you're applying for a position in industry, a non-profit organization or academia. So before agonizing over your letter, check to make sure it is needed at all. For example, cover letters are not part of the standard application package for some US federal government jobs, such as those at the US National Oceanic and Atmospheric Administration (NOAA). “I haven't seen a cover letter in years,” says Richard Merrick, chief science adviser for NOAA Fisheries in Silver Spring, Maryland. Similarly, they are not used in the highly specialized hiring process at Diamond Light Source, the United Kingdom's synchrotron science facility in Didcot. Diamond's chief executive, Andrew Harrison, explains that the organization aims to standardize the hiring process, because some candidates who work with headhunters may not write the letters themselves.

Some academic institutions also do not consider cover letters to be crucial. Yvonne Buckley, hiring lead for zoology at Trinity College Dublin, says that it is only a single component of an application package, along with a CV and teaching and research statements. But although hiring committees may not read a letter if the other materials provide all of the necessary information, she says, candidates should not necessarily abandon the practice of including one. Especially in academia, where CVs can run to many pages, a cover letter can help to highlight achievements that relate to the job description and point committee members to where they can find more specific or detailed information.

Negative attention

It is important to remember that there is no line-by-line blueprint for a successful application document, save the need to tailor it to the hiring organization and the specific position. And although standing out is desirable, you do not want to do so for negative reasons. Recruiters and hiring managers warn that you need to make sure not to kick yourself out of the running because of mistakes or missteps that you could easily have avoided (see 'Tips for effective cover letters'), such as addressing the letter to the wrong person, making typographical or grammatical errors or including inadvertent leftovers from a previous application. “If someone is unable to express him- or herself without errors, that is an immediate reject,” says Genest.

Another common issue is length. Outside academic environments, in which a two-page letter is common, recruiters emphasize that a carefully crafted one-page cover letter is enough. “A cover letter is not a book,” says Monika Lips-Sandmeier, a human-resources specialist at the Swiss Federal Institute for Forest, Snow and Landscape Research in Birmensdorf.

A catalogue of your accomplishments, or anything else, will also act as a black mark against you. “Lists are deadly,” says Genest. And although no one wants their application to be ignored, hiring managers warn that unorthodox attempts to stand out can backfire. At a careers fair, recruiter Lisa Knutson-Sealey once received a cover letter that was printed on fluorescent pink paper in bold type and a hard-to-read font. So, too, was the rest of the application. “It was just painful to look at,” says Knutson-Sealey, who hires researchers and others for the Washington State Department of Ecology. It shouldn't really be a surprise to learn that the candidate did not get an interview.