The Netherlands has this issue as well, points of income where your marginal gain is negative, ergo losing net money when making more gross money due to losing benefits. There are also indirect problems such as losing access to certain services (cheaper housing being one).
Obviously, this shouldn't be the case. Making more money gross should result in equal-or-more money net, without disadvantages, otherwise the incentive is gone.
It's in Dutch, but the most important columns are the first (gross income), the second to last (net income, including benefits) and the last (effective tax rate on the 1000 gross income increase).
Note the last column tells us that making 1000 gross extra will increase your net income about 100 between 32K and 31K gross income. Going from 31K to 32K will even make you lose money.
