certificate of completion; diploma
Official document proving that a course, program, or training has been completed. Often used in educational and professional contexts.
I received a certificate of completion at the end of the course.
Upon finishing this training, a certificate of completion will be issued.
認定証 is a certification of qualification or recognition, often for skills or standards, whereas 修了証 simply confirms completion of a course.
Compound of 修了 (completion of a course) and 証 (certificate). The reading is standard on'yomi.