At the risk of being somewhat boring ...

[AlfredJPruffock]

... does anybody happen to know how Social Security deductions are calculated in Belgium ?

[AlfredJPruffock]

Oopss ...

My apologies for being a tad lax - the answer to my question has been answered already in this very forum - by none the less then my dear departed friend Fleet - I have posted his wisdom here for the benefit of others - seek and ye shall find.

Social security in Belgium is actually just over 20%. I'd have to dig out some paperwork to find the exact percentage, but let's assume it's that.

It's 20% of your taxable income of three years previously. For the first three years, you pay a minimum contribution which is around €425 a quarter.
Then, after your taxable income for a given year is worked out by the authorities, you receive a Social security demand for the difference between what you have paid, and what you should have paid. This can be quite hefty, but in turn reduces your taxable income in the year that you pay it, which in its turn reduces the Social security contributions for the third year following it. This sounds silly and complicated, and it is, but that's the way things are.