Belgium has made changes to its social security collection process  meaning  that come 2015 self-employed workers in Belgium will have to calculate their Belgium social security contributions differently.

Currently it is possible  for a newly self-employed  person to make a provisional payment , subject to a minimum contribution level ,  based on the income of the third year that precedes  it . So contributions made  in 2014 would be based on a national income during  2011 as the actual net income may  not be  known at the beginning of the year  that the  provisional contributions  are made and an estimate can be used.

Currently freelancers have the option to pay only the minimum quarterly contributions during  their first three years  making it possible to defer payments and make up the difference between the amount paid and the actual liability at a later date. The changes to the rules mean that contributions will now be based on the actual net taxable income from the current year.

You can also check this article here to learn more about Belgium Social Security for contractors.

Under the new system however the self-employed person can request to decrease or increase their social security contribution in order to avoid large overpayments and the need for repayment and vice versa.

The current system can be  beneficial to freelancers where they have the option to  pay minimum contributions for the first three years when starting off. It can be very inconvenient in times of fluctuations in income as  the  full amount of any underpayment of social security from the previous year must be paid on top of any  contributions due  for the current year.