What the calculator uses
Three official tables for 2026/27, copied line by line from susi.ie: the undergraduate income thresholds and grant award rates, the postgraduate thresholds (fee contribution up to €4,500, special rate fees up to €6,270), and the PLC table. The logic is the same one SUSI publishes: pick the column for your number of dependent children, add €4,950 or €4,785 for every other family member in college, then test your income against the special rate, Bands 1 to 4 and the fee-only tiers in turn. Every threshold and rate is pinned by an automated test that fails if a number drifts from the source.