It is an extremely serious offence to stay beyond the limits of a visa in any country. The UK Border Agency, one of the largest law enforcement agencies in the UK, protects the country's borders, controls immigration and enforces penalties. Illegal immigrants face banishment periods of up to ten years, and their sponsors do not get off lightly either.
If an immigrant overstays his visa but departs the UK no later than 28 days after the expiration date, he will escape banishment penalties. If he stays beyond the 28-day grace period, various penalties will apply, depending on what happens next. If the immigrant leaves the UK voluntarily and covers all expenses of doing so, he will be banned from coming back into the country for one year. If he volunteers to leave the UK but is unable to cover the costs himself, he will be banned from re-entering the country for five years. Immigrants who have overstayed and try to hide this from the authorities face deportation and are not permitted to return to the UK for ten years. If visitors breach the terms of their visa, such as by entering the country on a tourist visa and then starting work, they face the ten-year ban.
Penalties also apply to those who have sponsored an immigrant who stays past the 28-day grace period. As of February 2013, sponsors who hired illegal immigrant workers faced a financial penalty of up to £10,000 per illegal employee, depending on what checks they had made, how often a warning or penalty had been issued to them and the extent of an employer's cooperation.
In 2012, legislation was tightened to clamp down on illegal immigrants. Before this, immigrants who had overstayed their visa could apply for a discretionary extension, which was judged on a case-by-case basis. From 1 October 2012, application for additional leave made after the 28-day grace period is automatically refused unless there is a strong human rights element to the case, or the immigrant is in a relationship or has a child with a UK or EEA national.
If you only have a short time on your UK visa, make sure you apply for an extension in time. If you have already gone past the 28-day grace period, you must leave the UK before submitting an application for another visa, and you will not be granted entry into the country until your new visa has been issued.