January 16 Individuals: Pay the fourth installment of 2023 estimated taxes (Form 1040-ES) if not paying income tax through withholding or not paying sufficient income tax through withholding. Employers: Deposit Social Security, Medicare and withheld income taxes for December 2023 if the monthly deposit rule applies. Employers: Deposit nonpayroll withheld income tax for December 2023 if the monthly deposit rule...
