Employers: For Social Security, Medicare, and withheld income tax, file IRS Form 941 for the second quarter of 2018. Deposit any undeposited tax. If your tax liability is less than $2,500, you can pay it in full with a timely filed return. If you deposited the tax for the quarter in full and on time, you have until August 10 to file the return.

For federal unemployment tax, deposit the tax owed through June if more than $500.

If you maintain an employee benefit plan with a calendar year end, file IRS Form 5500 or 5500-EZ for calendar year 2017.