Generally, a leased employee is the employee of an outside organization from which you lease the employee's services. For instance, you may use the services of a payroll clerk who is really employed by another organization; the other organization (the leasing organization) leases the services of its employee, the payroll clerk, to your business. Leased employees are not usually thought to include independent contractors.
If your business uses the services of leased employees and you want to adopt a simplified employee pension (SEP) for your business, you may use a prototype SEP or an individually designed SEP. Most financial institutions (and perhaps all brokerage firms) offer their own prototype SEP - one designed and customized according to their specifications and approved by the IRS. These prototype SEPs can be used by any employer.
For further reading, see Establishing An SEP IRA, SEP IRAs Tutorial and Plans The Small Employer Can Establish.
This question was answered by Denise Appleby