The concept of a social assistance agreement, its parties and purpose, which depends on the type of agreement, is defined. The system and mechanisms of concluding social assistance agreements as a basis for the formation of a non-state social security system are studied. The legislation does not contain a single list and mechanics of conclusion and execution. Under a social assistance agreement, the recipient, as a person in difficult life circumstances that he or she cannot overcome or mitigate on his or her own, may receive material benefits or other intangible benefits at the expense or with the participation of the provider under certain conditions. The purpose of concluding a contract is to assist in overcoming or mitigating difficult life circumstances at the expense of the provider's funds or property, or by raising funds or the provider's property, using non-state social security funds for a certain period. A person in need of social security has the right to use the assistance of a charitable organization in the form prescribed by law. On the basis of the agreement it is possible to receive services from volunteers and the volunteer organization. The probation volunteering contract is concluded to achieve the goal set by law, so it is advisable to set clear requirements for the probation volunteer. It is substantiated that the content of the inheritance agreement may stipulate the provision of social security to the alienator on the terms specified in the agreement. It is established that social security for children in difficult life circumstances can be provided by concluding social assistance agreements. The expediency of applying a foster care agreement to a child who has suffered from human trafficking, who has lost his or her parents or whose parents are unable to perform their duties due to health or other reasons in order to ensure that he or she is provided with social security under the conditions specified by law. The expediency of applying a foster care agreement for the immediate provision of family care for a child for a period when his family status is uncertain is indicated. It is substantiated that the purpose of the agreement on the placement of a child in foster care and cohabitation in a foster family is to provide him with social security and create conditions for learning and development. It is established that the purpose of the agreement on the establishment of a family-type orphanage is to guarantee the provision of social services and state assistance. On the basis of the conducted research the expediency of normative fixing of the standard form of the contract on rendering services of the municipal nanny that will promote coordination of interests of the parties of this contract and protection of their rights is proved. Keywords: contract, social assistance contract, purpose of contract, parties to contract, difficult life circumstance.