40% is a marginal rate. For the lower part of the income, you'll have a lower marginal rate. The effective rate is lower than the marginal rate. 23% is the rate

40% is a marginal rate. For the lower part of the income, you'll have a lower marginal rate. The effective rate is lower than the marginal rate. 23% is the rate of someone single and declaring 75k€ of net income (the marginal rate in this case is 41%). It seems that with such an income, you are part of the 3% wealthiers.