My W2 is not picking up my December payroll, it is short of 3100.

Thanks for notifying us of your concern, @deal1tc. Let's figure out why your December payroll isn't reflecting on your W-2.

In QuickBooks Online (QBO), you may notice that boxes 1, 3, and 5 have varying amounts or are different compared to your employees' pay stubs. In some cases, these differences are correct. Here are some common payroll situations and examples that can affect these boxes and state tax amounts on the W-2:

• Your employee has a pre-tax deduction, fringe benefit, or company contribution
• Your employee earns tips
• Your employee is exempt from one or more federal taxes

I recommend reading this article for the detailed explanation: Understand why W-2 box amounts are different.

However, it's best to reach out to our Payroll team so they can pull up your account securely and determine the root cause of the issue. They may also conduct a thorough investigation of this matter if necessary.

Furthermore, you may want to print your W-2s in QBO for your own records or send paper copies to your employees. 

Please don't hesitate to visit the Community again if you have additional concerns about payroll forms. I'll be here to assist you all the way. Take care.