Colorado Supplemental Tax Regulations for Google (Alphabet) RSUs
Colorado levies a flat 4.40% income tax rate on all taxable income. Employers withhold at 4.40%, meaning state withholding closely tracks true state liability.
Colorado Safe Harbor & Underpayment Penalties
Pay 100% of prior year or 70% of current year Colorado liability.
Employer Stock Plan Specifics: Charles Schwab / Morgan Stanley
Google utilizes a frontloaded monthly vesting schedule (33% across years 1 and 2). Because monthly vests are treated as supplemental wage distributions, Schwab withholds federal tax at flat 22%. Googlers with total comp above $350k find that each monthly tranche underwithholds by 10% to 15%, compounding silently over 12 months.
When vesting at Google (Alphabet), Charles Schwab / Morgan Stanley calculates automatic sell-to-cover withholding using Colorado's statutory supplemental rate of 4.40% combined with the federal supplemental rate (22% on up to $1M). Because top earners in Colorado reach marginal brackets exceeding these rates, you will face an incremental shortfall on April 15.
Localized CPA & Advisory Referral
Advisor Guidance: Connect with a Denver/Boulder CPA to ensure Colorado DR 0104EP quarterly estimates prevent underpayment interest.