A recent House of Commons Library research briefing has covered the issue of tax avoidance and evasion, alongside the measures the government has taken to tackle them. Whilst tax evasion is outright illegal, tax avoidance is a legal albeit disparaged practice in which individuals seek to reduce how much tax they pay in a manner not intended by the spirit of the law. Thanks to its legality, tax avoidance schemes can be marketed and supplied, although the government attempts to restrict and shut down these schemes through legislation. The research briefing covers some of this legislation that is more generalised than specific.
You can read the full briefing here.
