The Client Assignment Fee is what the client pays for your services at the top of the chain.
The Freelancer Assignment Fee is what your PSC charges Giant Business Connect for your services (excluding VAT) at the bottom on the chain.
You have 100% freedom to set your Freelancer Assignment Fee.The gap between those two fees needs to generate enough income for Giant Business Connect to cover all its costs and legal obligations for being the deemed employer, which include its own legal obligation to pay employers National Insurance and Apprenticeship Levy on your Freelancer Assignment Fee. Employers NI and AL are legal obligations on Giant Business Connect because it is the deemed employer (and Giant Business Connect is only the deemed employer because the the assignment is Inside IR35).
Only 1% of the Client Assignment Fee is for Giant Business Connect's costs, the rest of the gap is to meet its legal obligations as deemed employer. Giant Business Connect must also then withhold from its payment to your PSC the personal income tax and employees NI that you have to pay for being Inside IR35. This is based on the gross amount you set as the Freelancer Assignment Fee.
NB: Some figures rounded to the nearest pound.
Click here to see the calculator.