Every state taxes investors differently. Here is how Illinois treats capital gains at the top rate, the marriage penalty, estate and inheritance tax at death, municipal-bond interest, the §1202 QSBS exclusion, and a harvested loss — a plain reference to the state's tax code.
Illinois taxes long-term gains at a top effective 4.95%; a state estate tax; common-law step-up (only half of jointly-held property).
Loss treatment conforms to federal: capital losses net against gains and carry forward. Top effective long-term rate 4.95%.
A single flat rate regardless of filing status — marriage-neutral on rate; watch fixed-dollar exemptions and AGI thresholds.
Illinois estate tax: a $4,000,000 exemption — not indexed, administered by the Attorney General (Form 700), not IDOR, and not portable between spouses. It is a cliff threshold: once the estate clears $4M the frozen IRC 2011 state death-tax credit table (0.8–16% over 21 brackets) applies to essentially the whole taxable estate, so the first dollars over $4M carry a ~29% effective cost. Broad-raise bills are pending but NOT enacted — HB 2601 (to $8M) stalled in Rules; SB 2970's $6M applies only to qualified farm property — so $4M stands. Confirm the filing figure with counsel.
Taxes municipal-bond interest from every issuer — in-state and out-of-state alike. One of the few states with no muni-interest preference at all.
Conforms to IRC §1202 — the federal qualified small business stock gain exclusion carries through to the state return.
Capital losses carry forward under the federal Section 1212 rules — a harvested loss nets against gains and rolls forward until used.
Common-law (separate-property) state: at the first spouse's death only the decedent's half of jointly-held property steps up; the survivor keeps carryover basis on their half (IRC 1014(b)(9), 2040(b)).
Loss treatment conforms to federal: capital losses net against gains and carry forward. Top effective long-term rate 4.95%.
Illinois estate tax: a $4,000,000 exemption — not indexed, administered by the Attorney General (Form 700), not IDOR, and not portable between spouses. It is a cliff threshold: once the estate clears $4M the frozen IRC 2011 state death-tax credit table (0.8–16% over 21 brackets) applies to essentially the whole taxable estate, so the first dollars over $4M carry a ~29% effective cost. Broad-raise bills are pending but NOT enacted — HB 2601 (to $8M) stalled in Rules; SB 2970's $6M applies only to qualified farm property — so $4M stands. Confirm the filing figure with counsel.
A single flat rate regardless of filing status — marriage-neutral on rate; watch fixed-dollar exemptions and AGI thresholds.
Taxes municipal-bond interest from every issuer — in-state and out-of-state alike. One of the few states with no muni-interest preference at all.
Conforms to IRC §1202 — the federal qualified small business stock gain exclusion carries through to the state return.
Capital losses carry forward under the federal Section 1212 rules — a harvested loss nets against gains and rolls forward until used.
Coordinating how a portfolio is built and run against Illinois's rules is worth an estimated ~$40,000/yr for every $1M of taxable assets in our modeling — about +4.0%/yr after tax (a concentrated, naive book keeps ~1.8%/yr vs ~5.9%/yr tax-managed). Your actual figure depends on your holdings — the diagnostic computes it.
Tax law is only half the picture. How a portfolio is built and run — where each holding sits, how losses are used, how gains are timed — decides how much of Illinois's tax code you actually pay. An illustrative estimate for a portfolio here:
How this is modeled: a single 30-year proxy-spliced path (1996–2026), comparing a concentrated, high-turnover book with a tax-managed one — illustrative and coarse; treat it as directional, not a precise figure.
Five lenses turn Illinois's tax environment into a household decision — the same lenses every state is read through, so any two states weigh on identical terms.
The state takes 4.95% of every long-term gain at the top — moderate drag on what a realized return keeps.
A state estate tax exempts only $4M — far below the federal ~$14M; a cliff then taxes the whole estate, not just the excess; severe exposure at death that federal-only planning misses.
A harvested loss is worth the 4.95% state rate it offsets, on top of federal — moderate harvesting leverage.
Both the rate and the estate regime make relocation genuinely valuable — but domicile is a fact pattern, not a mailing address.
Common-law basis: only the decedent's half steps up at the first death — plan titling so the survivor is not left with low-basis lots.
Whether — and how — a change of domicile is worth pursuing, and the facts (days, home, ties) that make it real rather than nominal.
Whether the state's estate exposure warrants credit-shelter / QTIP titling or lifetime gifting to move value below the state threshold.
Setting a harvesting cadence that captures the state rate a banked loss offsets, sequenced against the state's loss-carryforward rules.
Placing the high-turnover sleeve in tax-advantaged accounts so the state's rate falls on the least of the household's realized gains.
State law reflects 2025 tax-year law; last reviewed 2026-07-07. Every classification is a summary of state law; where a primary-source citation has been verified, it is linked on the card.