An IRS Form 5305, Simplified Employee Pension — Individual Retirement Accounts Contribution Agreement is shown in New York on Monday, April 2, 2018. If small business owners want to set up the least complex retirement plans for their employees, the SEP, or Simplified Employee Pension, they can still do so by the due date for their returns. The owner must complete a formal written agreement to provide benefits to employees; the easiest way to do that is to complete IRS Form 5305. (AP Photo/Jenny Kane)