IL SB3376

Creates a "mark-to-market" tax requiring Illinois residents with net assets of $1 billion or more to annually recognize gains or losses on all assets as if sold at fair market value on December 31 of each tax year.

Applies to assets owned directly by the taxpayer, their spouse, minor children, trusts where the taxpayer is a beneficiary, and contributions to private foundations or donor-advised funds made within the preceding 5 years.

Limits taxable gains to a "phase-in cap amount" equal to 25% of net assets exceeding $1 billion, with taxpayers able to pay the resulting tax in one lump sum or over 10 annual installments (with a 7.5% annual deferral charge on later payments).

Provides credits for taxes already paid to other states on gains accumulated before becoming an Illinois resident, and allows net losses to carry forward indefinitely rather than being recognized in the year incurred.

Takes effect immediately, with initial mark-to-market calculations applying to taxable years ending on or after December 31, 2026, and revenue collected deposited into the General Revenue Fund.