Illinois Supplemental Tax Regulations for Apple RSUs
Illinois applies a flat 4.95% individual income tax rate with matching 4.95% supplemental withholding.
Illinois Safe Harbor & Underpayment Penalties
IL-1040-ES safe-harbor required if unpaid tax exceeds $1,000.
Employer Stock Plan Specifics: E*TRADE by Morgan Stanley
Apple vests typically occur in April and October. Employees receiving six-figure vests through E*TRADE will notice that statutory withholding leaves a 10%–15% federal gap when combined with base salary. Knowing exactly how many shares to sell prevents unexpected liquidation during market dips.
When vesting at Apple, E*TRADE by Morgan Stanley calculates automatic sell-to-cover withholding using Illinois's statutory supplemental rate of 4.95% combined with the federal supplemental rate (22% on up to $1M). Because top earners in Illinois reach marginal brackets exceeding these rates, you will face an incremental shortfall on April 15.
Localized CPA & Advisory Referral
Advisor Guidance: Work with a Chicago CPA to coordinate Illinois IL-1040-ES payments for large technology RSU vests.