Soldiers accrue leave at 2.5 calendar days for each month of active duty, per AR 600-8-10 — 30 days a year. Up to 60 days can be carried forward at the end of the fiscal year; anything accrued above 60 days is lost at the start of the new FY unless it is protected by Special Leave Accrual.
AR 600-8-10 governs leave and passes and sets the accrual rate by law.
Soldiers accrue leave at the rate of 2.5 calendar days for each month of active duty service.
AR 600-8-10, para 2-3a(1)
That works out to 30 days a year, but a balance does not accrue forever.
Soldiers may accrue and carry forward up to 60 days leave at the end of each FY.
AR 600-8-10, para 2-3a(2)
Accrued leave exceeding 60 days is lost at the start of new FYs unless protected by SLA or when a Soldier is in a missing status
AR 600-8-10, para 2-3a(4)
Leave also stops accruing during certain absences — AWOL, unauthorized absence, excess leave, and confinement under a court-martial sentence — under paragraph 2-3b of the same regulation.