I Have a question.. i got my w4 but last year i changed my marital status by error but i would like to put single.. what happens if my w2 says married then single

The changes that take place with your W4, whether you choose to use married or single is the amount of tax that is set aside for the year to meet your tax obligations. There is even a check box you can choose that labeled:  Married, but withhold at higher Single rate.

Here's what happens based on your selection.  

1. If you use single or married but withhold at a higher single rate, then there will be more federal (and possibly state) tax withholding from your pay check each pay period.  (Increased amount applied to you for the tax year)
2. If you use married you will receive more money in your pay check each pay period. (decreased amount applied to your tax year)
3. For every allowance or dependent you list less money is withheld and more money is in your pay check each pay period.

Summary, if you want to have a larger refund (or a lower tax due) you should use single and one or zero exemptions.  The lower wage earner (assuming both you and your spouse work) should most often use single and zero. The higher wage earner can use the same or choose married with a number of allowances (1 or 2).  This is based on what you want your results to be on the tax return, refund, higher refund or a lower amount of tax due with your return.  Your obligation is to have at least 90% of your tax liability paid to eliminate penalty for underpayment.

Check the information below.

https://ttlc.intuit.com/replies/3301783