Getting ready for the PSM I assessment
The PSM I assessment is an assessment offered by Scrum.org to certify a fundamental understanding of Scrum. The PSM I certificate is evidence of the holder's understanding of Scrum, as described in the Scrum Guide, and their ability to apply Scrum in Scrum Teams. There are no qualifications or preconditions needed to take the assessment. You don't need to take a Scrum.org course in order to take the assessment (though it would certainly help).
Scrum.org also offers two more Scrum Master assessments (PSM II and PSM III) that test more advanced Scrum knowledge. The assessment costs US dollars (USD) $150 and is taken online at https://www.scrum.org/professional-scrum-certifications/professional-scrum-master-assessments. You must be registered with Scrum.org to take the assessment. If you fail the assessment, you can retake it almost immediately. The $150 fee must, however, be paid every time you take the assessment.