Why did I get a letter saying there was a discrepancy about my state withholding?

Occasionally the discrepancy is on the employer side- they reported a different amount on the W2 than they reported or paid to the state.  If you receive a notice from the state, you should reply as they request- usually they will ask you to provide copies of your W2s to verify this information.  

.......beyond responding as AZ tells you to

.......Never trust the picture method, make sure you always confirm the entries for every box by editing the W-2 to make sure all is in the correct spot.  Pictures are not flawless, and sometimes $$ get stuck in the wrong boxes, or codes can be mis-assigned.