A Service Level Agreement (SLA) is an agreement between two or more parties and should clearly outline the roles and responsibilities of those involved in the agreement.
The SLA can be legally binding or an informal contract. The agreement may involve separate organisations, or different teams within one organisation. You might consider a service level agreement with a local facility, for example.
A cautionary note – an unincorporated club does not exist in law and therefore cannot sign contracts. If an unincorporated club does sign a contract, the contract will be legally valid and it will actually be the members of the committee who will have signed the contract and will be bound by contract law as to the outcome of said contract.
This places personal liability implications on committee members so consider incorporating the club before you sign any contracts for staffing, leases, service level agreements etc. This will protect committee members from personal liability.