以下是一份英文证明信的格式，可以根据实际情况进行适当调整：
[Your Name]
[Your Address]
[City, State ZIP Code]
[Country]
[Date]
[Recipient's Name]
[Recipient's Address]
[City, State ZIP Code]
[Country]
Dear [Recipient's Name],
I am writing this letter to confirm that [Name of the person you are writing the letter for] is [relationship to you, e.g. your employee, your tenant, your colleague, etc.] and has been [details of their involvement with you, e.g. working with you for a certain period, renting a property from you, etc.]. To the best of my knowledge, they have always been [details of their performance, e.g. punctual, responsible, hardworking, etc.].
[Add any additional details as necessary, e.g. if the letter is for a visa application, mention the purpose and duration of their visit, their financial ability to support themselves, etc.]
If you require any further information, please do not hesitate to contact me.
Sincerely,
[Your Name]
