A "statement of attainment" (SOA) is a document students receive verifying the units of competency they've completed as part of a nationally-recognised course.
In contrast to certificates, which are issued when a student completes a full set of study modules within a given course - SOAs are given when the student completes one or more of these units of competency, but not the entire list required for a full qualification. These documents essentially serve to showcase the specific units of competency a student has completed within a nationally-recognised training course.