A foal is registered in the foal book when:
- the dam is recorded in the foal book, studbook, Register A, or is registered with a recognized foreign studbook, and
- the sire:
- is approved or recognized by the KWPN, or
- is approved by a recognized studbook and meets the additional requirements, or
- is ranked in the top 10 of the WBFSH Sire Ranking.
The foal book is therefore the standard registration for foals whose parents both meet the requirements. From the foal book, a horse can later be entered into the studbook.