May 10 – Social Security, Medicare and Withheld Income Tax
File Form 941 for the first quarter of 2018. This due date applies only if you deposited the tax for the quarter in full and on time.
May 15 – Employer’s Monthly Deposit Due
If you are an employer and the monthly deposit rules apply, May 15 is the due date for you to make your deposit of Social Security, Medicare and withheld income tax for April 2018. This is also the due date for the non-payroll withholding deposit for April 2018 if the monthly deposit rule applies.