A Recruitment Agency is responsible for enforcing whatever decision the end hirer makes when determining a contractor’s IR35 status, and making sure their payments are processed correctly.
Assessing a contractor’s IR35 status is the sole responsibility of the end hirer. Even if the relationship has been fostered by a recruitment agency, the agency has no say in the assessment. However, they are obligated by law to help make sure the right payment process is applied based on that decision. This is because they will often be the fee payer if the contractor falls inside IR35 and have to deduct income tax and National Insurance from your invoice before payment.