What do employers look for in a writing sample?
Different employers look for different details in your writing sample depending on the job, company and industry. Every employer, however, will look for tone, style and writing skills including content, grammar, spelling and punctuation. While the specific writing style of the company can often be learned on the job, employers might be looking to hire someone with a certain level of writing skills at their first day on the job.
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https://www.indeed.com/career-advice/interviewing/guide-to-submitting-a-writing-sample