We recently had some cases where during their on board inspections, the German Authority inspectors of BG Verkehr asked for ballast water tank exemption documents.
Since according to the Ballast Water Management Convention vessels with 400GT and more need to have a Ballast Water Management Certificate along with a Ballast Water Management Plan and Record Book. Vessels being exempted are issued with a respective exemption certificate. However, small vessels generally don't have such.
Following the regulations of the German Authorities, small vessels (under 400GT) that don't carry ballast water tanks nevertheless are required to present a Ballast Water Tank Exemption document.
This document can be issued either by the classification society, certifying authority or Flag State where the vessel has been coded or classed. It is no certificate as such, rather a formal document of any of the aforementioned organisations stating that the coded/classed vessel does not include the capability to carry water ballast and isn't therefore likely to conduct an operation subject to the Water Ballast Management Convention. Hence, the vessel will not require to hold a Ballast Water Management Plan, or a Ballast Water Record Book.