HMRC have issued some guidance recently advising of the risk of using Non-compliant umbrella companies. Some umbrella companies offer higher take home pay often referred to as Enhanced or Advanced umbrella services. Frequently these are tax avoidance schemes, it is important to realise that the individual not the umbrella company is responsible for ensuring that they are paying the correct tax and national insurance contributions. Remember if it seems to good to be true, it is probably tax avoidance.

When using comparison sites or umbrella companies directly online, the web site may not be a legitimate business. You should always check to see if a company name, registered office and company registration number is shown and then check the information against Companies House records.

HMRC does not approve any umbrella companies.

https://www.gov.uk/guidance/comparison-and-broker-websites-marketing-umbrella-companies-are-not-always-what-they-seem-spotlight-55