The documents required to sponsor UK Visitor Visa include proof of accommodation and the sponsor’s bank balance. Also the sponsor should provide a letter of invitation for the trip to be undertaken by the visa applicant. The letter of invitation should be in accordance with Paragraph 35 Part I of the Immigration Rules. If your friends and family members are visiting the UK as a tourist or to attend your Graduation, they will need to apply online using the GOV.UK website. If you want to sponsor their visit to the UK you should produce an invitation letter and supporting documents.