I am getting my next paycheck on Jan 2nd, 2020. The paycheck covers work performed in 2019. Will the paycheck go towards my 2019 or 2020 401K contribution limit?
W-2 and 401(k) are based on the
Pay Date, not the
Period Beginning and
Period Ending dates.
Split things up would be a big complication.
Individual wage and 1099 employees always(?) whether they know it or not, use the cash method of accounting. According to IRS Publication 538 "Under the cash method, you include in your gross income all items of income you actually or constructively receive during the tax year."