How long am I exempt from counting days on an H-1B before the substantial presence test applies?

Unlike F, J, M, and Q visa holders, H-1B workers are not 'exempt individuals,' so you start counting every U.S. day for the substantial presence test from your first day on H-1B status. There's no grace period. In your first H-1B year you often pass the test partway through the year, making you a dual-status alien: nonresident before your residency starting date and resident after. In later full calendar years you'll almost always be a full-year resident alien if you live here. This differs sharply from students, who can exclude several years of days. The IRS lays out the rules for aliens in Publication 519. Track your exact arrival date, because it sets your residency start.