Employer for 5 years has been withholding on a married status incorrectly for 5 years. I have always been single when I file. Do I need to refile all my taxes for5 years?

[Elizabeth6]

Employer Error. 

I have been with the same company for 5 years. Upon new benefits provider start this year I noticed that my paycheck withholding is listed as "married". The issue is I have not been married for 5 years. It was never updated.

Do I need to notify the IRS? I have always filed my taxes as "single" as I am "single". Would all my previous tax years need a review? How would this affect my tax returns? And yearly refunds?

Thanks!

[Opus 17]

Your W-4 is used to calculate you tax to be withheld.  Your actual tax is calculated on your tax return, and the two things really have nothing to do with each other except that if you have too little withheld, you may owe a penalty and if you have too much withheld, you get a larger refund.  So you don't need to do anything at this point.

The effect of claiming married rather than single would be that a bit less tax would be withheld, resulting in more take home pay each week and a smaller refund.  If you change things up with your employer to single, all other things being equal, you would have more tax withheld and get a larger refund at the end of the year.