Entered an updated W2c as my company mis-reported income. Increase is around $800, but Turbotax is saying $9,500 due in tax. The $800 equates to $242 in additional tax.

Check these items:

• If you are doing an amended return, you must enter any amounts already paid or refunds received. 
• You should only have the w2c as income. The original w2 should not be on the return.