Illinois Supplemental Tax Regulations for Meta Platforms 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: Charles Schwab Stock Plan Services
Meta vests quarterly on the 15th of February, May, August, and November. With META trading at elevated fair market values, single quarterly vests can easily exceed $50,000–$100,000. If you do not proactively adjust your supplemental withholding rate in Schwab to 37%, you will owe thousands in underpayment penalties.
When vesting at Meta Platforms, Charles Schwab Stock Plan Services 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.