All boats need a valid Measurement Certificate issued by the Certification Authority of the MNA in their main country of residence and in the boat owner’s name. See Class Rules A.10,
For a certificate to be valid it should:
• Include the current owner’s details.
• Contain the registered sail number (not the sailor’s personal number)
• The owner needs to be a member of the National Association of the registered nation
• The registered sail letters and number should be engraved/on a plaque in the cockpit (Class Rule D 2.4 (b).
Please see here for Personal Sail Numbers.
OKDIA may act as the Certification Authority in specific circumstances and only with the permission of the MNA in that country and, if it exists, the National OK Dinghy Association.
This page is being updated. These are all the known countries where registered OK Dinghies exist.
| Nation | Certification Authority | Further info |
| ARG | OKDIA | OKDIA is recognised as the Certification Authority |
| AUS | ||
| AUT | ||
| BEL | ||
| BRA | OKDIA | OKDIA is recognised as the Certification Authority |
| CAN | OKDIA | OKDIA is recognised as the Certification Authority |
| DEN | ||
| ESP | ||
| FRA | ||
| GBR | Royal Yachting Association | https://www.rya.org.uk/membership/membership-benefits/rya-class-certificates |
| GER | Deutsche Segler-Verband (DSV) | https://www.dsv.org/ |
| IRL | OKDIA | OKDIA is recognised as the Certification Authority |
| ITA | OKDIA | OKDIA is recognised as the Certification Authority |
| LUX | Yacht Club Luxemburg | |
| NED | Koninklijk Nederlands Watersport Verbond (KNWV) | https://www.watersportverbond.nl/ |
| NOR | ||
| NZL | NZOKDA | https://www.okdinghy.co.nz/ |
| POL | ||
| SUI | ||
| SWE | ||
| THA | ||
| USA | USOKDA | https://usa.okdinghy.org/ |