Let the Past be Past
Kent R.
I'll get right to the point. Using the correct tense on your resume is way more important than you probably think. Adhering to proper grammar is critical on your resume, so that alone is reason enough to ensure your are using appropriate tenses. But there are other reasons to be careful with tenses…
Using appropriate tenses makes your resume more reader-friendly, and the more reader friendly a resume is, the more likely it will actually get read! Even more importantly, using incorrect tenses, such as listing past positions in the present tense, can make even the most achievement-focused bullet points and position overviews read impersonal – like the information you are providing doesn't belong to you but is more generally about the role.
Here is the long and short of it: Past positions, completed projects, and finalized achievements belong in the past tense. Your current position and on-going projects can be in the present tense.