| December 2021 | |
| December 10 | Employees who work for tips – If you received $20 or more in tips during November, report them to your employer. You can use Form 4070. |
| December 15 | Corporations – Deposit the fourth installment of estimated income tax for 2021. A worksheet, Form 1120-W, is available to help you estimate your tax for the year. |
| Employers Social Security, Medicare, and withheld income tax – If the monthly deposit rule applies, deposit the tax for payments in November. | |
| Employers Nonpayroll withholding – If the monthly deposit rule applies, deposit the tax for payments in November. | |