My acquaintance from a certain country wanted to work as a computer engineer in Japan and applied for a certificate of eligibility years ago, but his application was denied. He contacted me after his application was denied.
He graduated from neither a university or a professional training college. If an applicant graduated from either one, applying for an Engineer/Specialist in Humanity/International Service is relatively easy, but an applicant might be still eligible if he or she has 10 years of practical experience in the field (3 years for International Service) even if he or she has not graduated from either a university or a professional training college.
If an applicant wants to prove 10 years of experience, and he or she has worked at more than one company, each company he or she has worked at must issue the employment certificate. This sounds somewhat easy, but if a company the applicant has worked before closed or went bankrupt, the certificate cannot be issued.
My acquaintance above could not obtain certificates and consequently was ineligible. If a person wishes to work in Japan under an Engineer/Specialist in Humanity/International Service in the future after 10 years of experience, he or she should start preparing carefully early enough.