I started working for a company in December on Dec 10 and I got paid in January because I wasn't on Payroll , my employer deposited the check into my account. I am wondering since there is no W2 associated with my account, should I report it in my 2016 tax filing season or in 2017 as I got paid in 2016? I am in California.
For most Americans the date on the check determines the tax year.
A check with the date of Jan X 2016 will be reflected on the tax forms you will file in early 2017. That also means that the 401K money is also 2016 money, and so is the money for the flexible spending account, or health savings account.
The change of year impacts everybody differently. That last/first check can make a big difference for some people. If you are trying to make sure you deposit the maximum amount of money into one of those accounts, knowing how many pay checks there is in the year is important. It also works the other way, getting an extra check can cause you to over deposit into those accounts.
The taxes for that Jan 2016 paycheck are collected by your employer and periodically sent to the appropriate government office. You are paying those taxes on payday, even though you won't file that paperwork until 2017.