Annual Gross Salary 55,440 Euro in Belgium for a freelancer in IT

So if you are a freelancer (not as a sprl company), then you can normally simply expect to chop your daily rate in two - 110 for you, 110 for 'them'. This is a fairly safe rule-of-thumb. That's assuming you will be setup with a Belgian vat number, and you are being correct and honest about your expenses, and you have opted to pay the full amount for social security each quarter. It's easier and normally financially beneficial if you find a good accountant to take care of everything - but they can typically cost 2k per year.

Your gross salary estimate seems like too much because there are 260 potential working days per normal year, minus national holidays which your employer probably won't let you work, and you will probably need to take 'personal holiday' days for various reasons. So I doubt you'd work 252 days per year?? ..Unless you will be able to work 6 days per week maybe?

So per month as a net amount I would guess you would take home closer to 2200 EUR
on average.

Have you already signed? How much experience do you have?