ICAS assessments are delivered online through the Janison Replay platform and consist of multiple-choice questions along with some free-response items depending on the subject. Each paper is timed, typically running 45 to 60 minutes, and is sat under supervised conditions at the student's school during the official testing window.

ICAS is administered annually during a set testing window, usually between August and October in the Northern Hemisphere sitting. Exact dates vary by subject and country, and participating schools choose specific sitting days within the official window published by Janison each year.

Registration fees typically range from about $15 to $25 USD per subject, though pricing is set by each participating school and may vary by region. Students register through their school coordinator rather than directly with Janison, and schools handle payment collection and test scheduling.

ICAS is offered to students from Year 2 through Year 12, which corresponds roughly to ages 7 through 18. Different papers are tailored to each grade level, with age-appropriate content and difficulty scaling progressively from elementary through high school stages.

Every participant receives a printed certificate and an online results report showing their raw score, percentile rank, and performance band. Bands range from Participation through Credit, Distinction, and High Distinction, with the top 1 percent of scorers in each region awarded a Medal.

ICAS is held only once per year per subject, so students cannot retake the same assessment within the same testing cycle. However, they are free to register again the following year, and many students sit ICAS across multiple years to track academic growth over time.

Calculator policies depend on the grade level and specific paper. Lower primary Mathematics papers generally prohibit calculators, while some upper secondary papers permit basic scientific calculators. Students should confirm the exact rules with their school coordinator before the test day to avoid disqualification.

ICAS measures higher-order thinking and problem-solving skills for high-achieving students, while Reach is designed for a broader range of abilities and provides detailed skill-level feedback. Both are developed by Janison, but ICAS is competitive and awards certificates, whereas Reach focuses on diagnostic insights.