A contract of service is an agreement between an employer and an employee. In a contract for service, an independent contractor, such as a self-employed person or vendor, is engaged for a fee to carry out an assignment or project.he agreement can be in writing, verbal, expressed or implied. It can be in the form of a letter of appointment or employment, or an apprenticeship agreement. However, to minimise disputes on the agreed terms and conditions, the contract should be in writing.