If a visa expires and no extension or new application has been submitted, expats immediately lose their legal right to live, work, or study in the UK. For expats, this situation is known as overstaying and can have serious consequences. Expats in the UK who overstay even by a short period may face fines, detention, removal from the country, and bans on returning in the future. Overstaying can also damage future visa applications, as it is recorded in immigration history and viewed negatively by the Home Office. In some limited cases, expats may be protected if they submitted a valid extension or visa-switching application before their visa expired, as their rights continue under “section 3C leave” while a decision is pending. Expats in the UK should never ignore an expiry date and should plan months in advance to extend, switch, or leave the country lawfully. If a visa has already expired, expats should seek urgent legal advice, as acting quickly can sometimes reduce long-term immigration consequences.