You must carry onboard: 
Tide tables 
International regulations for preventing collisions at sea

Certificate of competence: 
On Belgium inland waters the skipper of a vessel over 15m in length or capable of more than 11 knots must have an ICC

Entry from a non-Schengen country: 
A border free agreement, known as the Schengen Agreement, exists between 15 countries (Austria, Belgium, Denmark, Finland, France, Germany, Iceland, Greece, Luxembourg, Netherlands, Norway, Portugal, Spain and Sweden). A crew list form must be completed for any vessel entering Belgium from outside these countries. Samples of the form are available to download, however on arrival in Belgium you may be asked to discard such printed forms and complete a self carbonating triplicate form instead.

Other: 
A registration plate is required for all Belgian yachts and for visiting craft staying for more than two months. Navigation dues are then payable for all yachts over three tons.  Taxes and payments on the Belgian inland waters differ between the north and south of the country. In the north and east a tax disc must be displayed and in the south and west payment is by the journey using a Permis de Circulation which is issued and stamped at most locks. Charges are reported in both systems to be modest.  Foreign yachtsmen entering Belgium by canal should report to the first navigation tax office and on leaving should report at the last lock.