Do E.U. employees pay tax on their salaries?
They only pay a special E.U. tax.
As a European civil servant, your salary is not subject to national income tax. Instead, salaries paid by the Commission to its officials are directly subject to a Community tax which is paid directly back into the EU's budget. This tax is levied progressively at a rate of between 8% and 45% of the taxable portion of your salary. An additional special levy is in place until 2012 (see Article 66 of the Staff Regulations ).
Do you know if this is a similar rate of taxation(in euros) if they paid directly to the Belgian treasury?
@user357320 Sorry, no; I don't know the Belgian tax system. Probably it depends on the exact situation.