Longman Dictionary of Contemporary English
self-certification
noun
EXAMPLES FROM CORPUS
▪ Medical certificates should be forwarded directly to the course director or senior course tutor. Self-certification will not be accepted.
Wiktionary
self-certification
n. (context UK English) The act of an employee certifying that he was absent from work due to sickness, and is eligible for statutory sick pay
Wikipedia
Self-Certification (New York City Department of Buildings)
Self-Certification, officially known as Professional Certification, is a process by which licensed professionals may bypass a full review of a building project by the New York City Department of Buildings.