By default, the spelling and grammar check in Microsoft Word 2010 and 2013 does not check for sentence spacing, allowing you to use either one or two spaces after a period without prompting a warning. To ensure your documents have a consistent spacing, set the number of spaces required in the grammar check settings and then run a full check or watch for blue underlines, which indicate formatting inconsistencies. Tips Writer Bio

How Do I Check Sentence Spacing in Word  - 39