In Germany, the mandatory minimum height for boat registration numbers on small vessels is 10 cm. The marking must be permanent, clearly visible, and easily legible. Latin letters and Arabic numerals are required, and they must be clearly distinguishable from each other.
The registration number must be affixed on both sides of the bow or stern. Alternatively, for suitable boats, placement solely on the transom is also permitted. The key requirement is that the registration number must be visible from the outside at all times.
A strong color contrast is also required: light lettering on a dark background or dark lettering on a light background. This ensures legibility even in changing light conditions, rough water, or from a greater distance.
Note: In Switzerland, a minimum letter height of 8 cm applies for vessels up to 15 m in length.
