Dear Sir, Thank you for your letter of [1st April] about my application for a visa [reference xxxx]. As requested, I enclose my medical certificate attested by the UAE Embassy at Colombo. [[ Please let me know when you will be able to issue the visa. ]] Yours sincerely, .... The last sentence is probably unnecessary --- unless you know it will be a long time. However, you do need to include the reference number of your application --- or the equivalent.