I changed job within the same company. (large corporate). I got 2 W2s with the same EIN number and I have an excess social security withheld ($4000)
The HR and Payroll department cannot be reached and cannot reimburse me or send me a corrected W2.
Can I take a credit of the $4000? . line 71 on form 1040?
No, do not take the credit on line 71 of your 1040. The procedure is different if the excess was taken my one employer. See excerpt from the this FAQ on the topic Can I get a refund for excess SS tax withheld?
What if my employer can't – or won't – cooperate?
You can correct the Box 4 amount yourself before filing. Simply multiply the amount in Box 3 by a factor of 0.062 and enter that amount or 7,886.40 (whichever is less) in Box 4.
To get a refund for the excess withholding, fill out IRS Form 843: Claim for Refund and Request for Abatement according to the Form 843 Instructions and mail it in separately. Make a copy to keep with your tax return paperwork.