Belgium is
the highest taxed OECD country by a substantial margin when looking at total tax wedge. Far higher than the Scandinavian countries for an overall tax wedge of 55.3% of labour costs (2015) [1]. For comparison the next two are Austria at 49.5% and Germany at 49.4%. Sweden 42.7%. Norway is at 36.6%, Denmark 36.4%.
The thing is you obscure it with an unusually high employer social security contribution.
But even looking at "just" income tax and employee contributions on an average salary, Belgium ends up at 32.4% of total employee costs (so these numbers are lower than the percentages paid of gross salary) vs. Norway with 25.2%, Sweden with 18.8% and Denmark at 35.8%.
If you instead of looking at total labour costs, you look at gross wages, Belgium is at 42%, vs Denmark 36%, Norway 28.4%, Sweden 24.7% (for comparison: US: 25.6%). This also places Belgium as the highest taxed OECD country,
Denmark is the extreme opposite of Belgium, in that Denmark has extremely low employer social security contribution and no employee social security contributions (it's baked into the income tax).
[1] http://www.keepeek.com/Digital-Asset-Management/oecd/taxatio...