Proofreading, quite simply, is the stage of writing where the document is gone through with a fine-tooth comb, in order to check for any remaining errors in the text. This is the final stage, before anything is published to print, or online, or is sent or posted. This is to ensure that the final produce that is going to be read is error-free and as perfect as possible.

A professional proofreader will meticulously check a finished piece of text for a variety of mistakes that may remain. Many online proofreading services will have the experience and expertise to look out for common errors, which include correcting the following:

1.    Typing errors that still make words
These are often missed, as spell check won’t catch them as being incorrect; examples include from/form, it's/its, thing/think.

2.    Typing errors that are not words
These occur frequently when spell-check is not used, resulting in not even the obvious typing errors being picked up by spell-check.

3.    Words that can be easily confused
Even proofreading professionals may get muddled up when it comes to confusing word choices, and may need to double check usage of words such as affect/effect, and lie/lay.

4.    Repeated words
It is easy to overlook ‘and and’ or‘the the’, especially if they are separated by a line break. Though be careful of spell check, as it may flag a repeated word and suggest deleting it, when in fact it is necessary for the sense of the sentence.

5.    Sentence fragments
Verbs not operating as verbs and sentences too short or too long to easily identify their structure are common examples of this.

6.    Incorrect pronoun-antecedent use
It is important for pronouns to correspond with the number, person, and gender to which they refer. This means checking for correct plural and single usage, and gender terms such as he/his/him and she/hers/her.

7.    Punctuation problems
It is understandably common to not notice missing full stops, or misplaced apostrophes, along with incorrect comma usage and missing quotation marks. When a writer is focusing on the content of the text she is writing, these smaller details can be easily lost.

8.    Consistency
One of the most important things to check for is the consistency of the text. In particular, this refers to spellings, it is not uncommon for a word or name to have several spellings depending upon the writer’s preference, whereas it is true that these multiple versions are correct, it is important to pick one spelling and stick with it throughout the document.

9.    Formatting
Checking to make sure that all the paragraphs are indented accordingly and equally, that all font sizes and styles correspond consistently, and that any pictures are positioned correctly with the correct captions can make a huge difference to the readability and look of a document.

On the surface, proofreading may sound fairly simply: checking for errors in a document. However, as this list demonstrates there is a little more to it than that and requires a great deal of focus, attention, and linguistic knowledge. Yet, this extra effort is well worth the time, as good writing speaks volumes. When a reader is getting distracted by errors in a document, they may struggle to fully grasp the message within the actual content. Furthermore, they may feel that the mistakes represent the author’s attitude towards the work, thus undermining the author’s credibility.