Why do you need help on English check or proofreading? Or even copy-editing for that matter? Let people who don´t have time go to a proofreading agency. You have the time; can´t you do the English check yourself? Questions like this often come up when you are advised to have your article or paper sent for copy-editing or English check. It is true that when you read your document for this sole purpose, you spot and correct the mistakes. Is it a comprehensive proofreading exercise? Should you run it through professionals? And why? The answer lies in "errors". An error is something that you do not recognise. Hence, while you correct a mistake, you do not correct an error as you do not know a correction is needed. You need a teacher or a professional agency engaged in copy-editing to locate them (Gass & Selinker, 1994). Any professional agency in the business vetting documents has to cover various types of errors, besides the mistakes which you have overlooked when you did the exercise. The agency you choose should help you get your document back free from grammatical, Syntactic, lexical, semantic & substance besides any organisational errors.