you mention that NIC1 is based on cash earnings. If somehow in the question there is also a personal contribution, occupational pension scheme or a PAYE figure . Do we have to deduct these from the cash earnings ?
Also, for NIC2 we pay 2.85 pounds / week for all the trading profit and not what exceeds the threshold of 6025 pounds?
The cash earnings is the gross figure before deductions that are allowable for income tax purposes like a pension contribution and of course before the income tax (PAYE) figure itself. Yes it is a single amount per week irrespective of excess above small profits threshold – it is the Class 4 figure that is linked to the level of profit