Ideally you will have a written and signed contract. But you may have other documentary evidence. You will also want evidence that you fulfilled your side of the bargain (e.g. a signed delivery note). It will be helpful if there is clear evidence that you made the customer aware of your terms and conditions before the contract was agreed.Ensure, also, that you keep copies of any correspondence you send while chasing the debt or attempting to negotiate a compromise.Discuss the quality of your evidence with your solicitor before taking court action, particularly if there is a dispute over the debt.