I have a client who got a W-2 from a third party for sick pay for the amount of $7851 Wages.  The W-2 states the Social Security wages were $1252. 

My client had to pay back all but the $1252 that was stated in the SS wages.  When my client contacted the third party asking them to correct the wage amount, they said that they would not.  They stated that a letter they sent stating that the $6599 wages return was sufficient. 

Does anyone know how what I have to do so the $6599 is not taxable to my client.

Thanks