Harbour dues 
Harbour dues are charged for the use by sea going vessels of the Rotterdam harbours. For all vessels  the Gross Tonnage (GT), stated on the International Tonnage Certificate (ITC) 1969, will be accepted as a basis for the calculation of harbour dues.
The harbour dues for sea going vessels are due for a period of time of 2 months maximum for a stay in one or more ports within the Moerdijk / Rotterdam area. After this time period the tariff for laid-up vessels is applicable.

Special reductions

Green Award
The so-called Green Award certificate is issued by the Green Award Foundation to shipping companies whose ships and management both comply with rules and environmental regulations laid down by the Foundation. 

The Port of Rotterdam Authority allows a premium (= discount) of 6% on paid harbour dues to oil and product tankers (except combination carriers and chemical tankers) with a Green Award certificate. This premium is calculated after any deduction for SBT restitution. 
More information: www.greenaward.org

Agribulk
For agribulk vessels ≥ 10,000 GT frequency reduction can be applicable.