Applicants who fear that their bank statements may betray a weak financial position will sometimes resort to a ['parking' strategy][1]. This strategy involves having a relative or other trusted party placing a large sum of money in the applicant's account temporarily so that the applicant's bank statements look better. It's a popular strategy, but when it fails, the application is refused and the applicant's credibility is damaged. It is the applicant's responsibility to show that funds available for the visit are his and available to him for the visit. This is stated in <del>Paragraph 41 of the rules </del> (see update below). In your case it looks like the ECO decided you wanted to appear more prosperous than you are, so you found someone to park money in your account. Moreover, he was unable to use a previous history to help determine if you are a reliable and compliant person. Irregular bank transactions need to be carefully documented with paperwork that shows \[1\] who, \[2\] what, \[3\] how, \[4\] when, and most importantly \[5\] why. If you recently sold a house for example, they would want to see the complete transaction history, up to and possibly including the bank statement of the counterpart. The only remedy available is to make a fresh application. You need to prepare the application knowing that your credibility has been damaged and they will apply more scrutiny and caution when they make their decision. Update ---------- Owing to a rule change in 2015, the rule is now stated in [Appendix V Paragraph 4.2 subparagraph e][2] > must have sufficient funds to cover all reasonable costs in relation > to their visit without working or accessing public funds. This > includes the cost of the return or onward journey, any costs relating > to dependants, and the cost of planned activities such as private > medical treatment. The ways that an applicant can meet the rules and provide the appropriate evidence is given in [Visitor: supporting documents guide][3] Related article: https://travel.stackexchange.com/questions/51849/hidden-requirements-in-uk-visa-applications-source-of-evidence-of-funds [1]: https://travel.stackexchange.com/questions/62411/what-is-funds-parking-in-the-context-of-uk-visa-applications [2]: https://www.gov.uk/guidance/immigration-rules/immigration-rules-appendix-v-visitor-rules [3]: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/423699/2015_04_20_Visitor_Supporting_Documents_Guide_-_Final__2__-_CLEAN.pdf