There is no set form of words for a letter of invitation. Sponsors should write the invitation in their own words. It should be addressed to the person being invited and must include details of the purpose and duration of the visit and also the relationship between the applicant and the signatory of the letter and /or the persons inviting the applicant. These letters do not have to be notarised. Essentially, it should be clear from the invitation why the person is being invited, by whom, for how long and where they will stay.