Chancellor Philip Hammond announced in the Budget that the rate for Class 4 NICS would rise from 9% to 10% in April 2018 and to 11% in 2019.
That compares to 12% currently paid by employees.
The chancellor said that this would raise £145m a year by 2021-22. On its own, the change announced in the Budget will leave 2.84 million people facing an average annual increase of £240.
Class 2 payments which have a lower threshold of £5,965 or more in profits a year will be abolished.
Taken together, only the self-employed with profits over £16,250 will have to pay more as a result of these changes at an average cost of 60p a week to those affected.
The chancellor said this brought more fairness between the self-employed and employees.