I have googled this but am none the wiser. I have just signed up with three supply agencies, two of whom are insisting I have to be paid through their recommended umbrella company (the other has payroll but pays a pittance). Having accepted my first assignment today I rang the umbrella company to check a few details and discovered that not only do I have to pay them a fee, but I have to pay employer's NI in addition to employee's NI. I have never heard of this before. I will be employed by them so why must I pay their contribution as well as my own? I had thought I had negotiated a reasonable daily rate but this puts a new perspective on things, and I am unsure how to work out how much I will pay. As I understand it, NI is paid on any weekly income over £162 at a rate of 13.8% for the employer and 12% for the employee. Does this mean I pay a whopping 25.8% before my tax comes off as well? Or am I looking at this wrong? Hoping some sympathetic tax-savvy teacher can help me out.