Individual Tax Returns (1040) for Startups and SaaS in Chicago

Preparing a founder individual tax return in Chicago is a different exercise from preparing an ordinary 1040, because for a startup founder the return is driven by equity rather than wages, and a startup CPA builds it around the cap table instead of around a paycheck. Most founders draw a deliberately small salary in the early years so the company can preserve its runway, and that salary flows onto the return the normal way, subject to federal tax and the flat 4.95 percent Illinois income tax. The complexity comes from everything else, the option exercises, the stock sales, the vesting events, and the fundraising instruments that touch a founder personally, and those are the items that make the return demanding to prepare correctly.

The first job is to gather the equity picture in full. That means the grant documents for founder stock and options, the strike prices and exercise dates, any 83(b) elections that were filed, the vesting schedule, and records of any shares sold, whether in a secondary transaction or at an exit. Each of these has a distinct tax treatment. Founder stock with a timely 83(b) generally produces no ordinary income at vesting and sets up capital gain on a later sale. Nonqualified options produce ordinary income on the spread at exercise. Incentive stock options produce no regular income at exercise but create an alternative minimum tax adjustment. A stock sale produces capital gain or, if the shares are qualified small business stock, a gain that may be excluded. Getting each item onto the return under the right rule is the core of the work.

The Illinois layer is comparatively simple because the state uses a single flat rate of 4.95 percent and begins from your federal taxable income, so most of the federal treatment carries straight through to the state return. Illinois does not impose its own alternative minimum tax, which limits the state consequence of an ISO exercise, and it generally follows the federal exclusion for qualified small business stock, which is a major benefit at an exit. There is no separate Chicago city income tax on wages, so the city does not add a personal income layer on top.

Here is a concrete example of why the equity focus matters. Suppose a founder draws a $60,000 salary and, in the same year, exercises nonqualified options with a $400,000 spread. The salary is minor next to the equity, and the $400,000 spread is ordinary income taxed at the founder’s federal rate plus 4.95 percent Illinois tax, roughly $19,800 to the state on that single event. A return prepared as though the salary were the whole story would badly understate the tax and leave the founder facing a large balance plus penalties. We prepare the founder 1040 around the equity that actually drives it and coordinate the planning through our tax strategy consulting service. The federal return framework is described by the IRS Form 1040 guidance, and the state rules sit with the Illinois Department of Revenue.

Stock options are one of the most consequential items on a Chicago founder individual tax return, and how they are taxed depends entirely on which kind of option you hold, so a startup CPA has to separate them carefully before touching the 1040. There are two types, and they behave in opposite ways at exercise. A nonqualified stock option is taxed at the moment you exercise it. The spread between what you pay to exercise, the strike price, and the fair market value of the shares on the exercise date is treated as ordinary compensation income, taxed at your federal rate and at the flat 4.95 percent Illinois rate, and it is usually subject to withholding through payroll.

An incentive stock option works differently and contains the trap. When you exercise an ISO and hold the shares, you recognize no regular taxable income, which sounds like pure good news. The catch is the alternative minimum tax. The bargain element, the same spread between strike and fair market value, is an adjustment item for the federal AMT, so even though you owe no regular income tax on the exercise, you can owe federal AMT on that spread. Because the AMT is calculated on value you have not sold, a founder who exercises a large ISO grant and holds illiquid startup shares can face a real federal tax bill in April on a paper gain, with no cash from the shares to pay it. That is the AMT trap, and it has caught many founders who exercised late in the year without modeling the consequence.

Illinois softens the state side of this. Because Illinois begins from federal taxable income and does not impose its own alternative minimum tax, an ISO exercise that creates a federal AMT adjustment generally does not create a matching Illinois tax, so the state exposure on an ISO exercise is limited under the flat-rate system. A nonqualified exercise, by contrast, does flow to Illinois, because the spread is ordinary income that Illinois taxes at 4.95 percent along with the rest of your income.

Here is the math that shows the trap. Suppose a founder exercises incentive stock options with a $300,000 spread and holds the shares. For regular federal tax there is no income, and the Illinois consequence is minimal because the state has no AMT. But the $300,000 becomes an AMT adjustment federally, and depending on the rest of the return that can produce a federal AMT bill in the tens of thousands of dollars, owed in April on stock the founder cannot yet sell. Contrast that with exercising nonqualified options with the same $300,000 spread, where the founder owes ordinary federal tax plus about $14,850 to Illinois, but at least the character is clear and withholding usually applies. We model the AMT before any ISO exercise, size the exercise to what the founder can absorb, and time it to avoid an unfundable bill, coordinating with our tax strategy consulting team. The option rules are laid out in the IRS stock options guidance and the IRS alternative minimum tax guidance.

Qualified small business stock is the single most valuable thing that can appear on a Chicago founder individual tax return, because when the requirements are met it can remove federal tax, and effectively Illinois tax, from an enormous gain, so a startup CPA treats the QSBS analysis as one of the highest-stakes parts of the return. Section 1202 allows an eligible shareholder to exclude a large portion, in many cases the entire amount, of the gain on a sale of qualifying stock from federal income tax, up to a generous per-issuer cap. For a founder who built a company and sells for millions, whether the stock qualifies can be the biggest single line on any return they ever file.

The Illinois treatment follows the federal result in the founder’s favor. Illinois computes state income tax starting from federal taxable income, so a gain that is excluded federally under Section 1202 generally is not added back into the Illinois base. That means a qualifying Chicago founder avoids not only the federal tax on the gain but also the flat 4.95 percent Illinois tax that would otherwise apply. Illinois does not have a separate mechanism that claws the excluded gain back, so the founder keeps the full federal benefit at the state level, which makes the exclusion even more powerful for a Chicago resident than the federal savings alone suggest.

The difficulty is that qualification is decided by facts locked in long before the sale, and the return preparer can only report what the history supports. The company had to be a domestic C corporation. Its gross assets had to be under the statutory ceiling when the stock was issued. The stock had to be acquired at original issuance, meaning directly from the company rather than bought from another shareholder. The company had to run an active qualified business, which covers most software and SaaS companies. And the shareholder generally had to hold the stock for the required multi-year period, measured from the issuance date. This is why the 83(b) election filed within thirty days of the original founder grant matters so much, because it fixes the issuance and starts the holding-period clock that the exclusion depends on.

Here is the concrete math. Suppose a founder sells qualifying QSBS for a $5,000,000 gain after satisfying every requirement including the holding period. Under Section 1202 that entire gain can be excluded from federal income tax, saving roughly $1,000,000 at a 20 percent federal capital gains rate, and because Illinois conforms through its federal starting point, about $247,500 of Illinois tax at 4.95 percent is avoided as well, for a combined saving near $1,247,500. Now suppose the founder had formed as an LLC first and converted late, restarting the clock and selling short of the required holding period. Both exclusions are lost and the full $5,000,000 is taxable at both levels. We report the sale, apply the exclusion correctly, and maintain the documentation proving the shares qualified, building on the record we start at entity formation and structuring. The statute is at 26 U.S.C. Section 1202, and the state conformity sits with the Illinois Department of Revenue.

A Chicago founder needs to make estimated tax payments because the equity events that dominate a founder individual tax return often carry little or no withholding, and the tax system expects tax to be paid as income is earned rather than in a lump at filing, so a startup CPA sets up quarterly payments to keep the founder both penalty-safe and able to actually pay the bill. A salary has income tax withheld from each paycheck, but an option exercise, a secondary stock sale, or restricted-stock vesting frequently generates far more tax than any withholding covers, and the shortfall is the founder’s responsibility to pay through estimates. This is a structural feature of how founders are compensated, not an occasional wrinkle, so it has to be planned for every year the cap table is active.

The federal system provides a safe harbor that determines whether you owe an underpayment penalty. You avoid the penalty if your payments during the year total at least 100 percent of last year’s total tax, or 110 percent of last year’s tax if your prior-year adjusted gross income exceeded $150,000. Illinois runs its own quarterly estimated-tax system alongside the federal one, applying the flat 4.95 percent rate. The 2026 federal due dates are April 15, June 15, September 15, and the final one on January 15, 2027, and Illinois generally follows the same quarterly schedule, so a founder is managing two parallel sets of payments through the year, one to the IRS and one to Springfield.

The important distinction, and the one that trips founders up, is between avoiding the penalty and paying the actual tax. Meeting the safe harbor based on a small prior-year tax protects you from the penalty, but it does not mean you have paid what you owe. If this year includes a large equity event, the real tax on that event still comes due at filing, and a founder who relied on the safe harbor and spent the proceeds can be caught with a large April balance. Planning has to cover both the penalty protection and the cash to settle the true liability, because those are two separate numbers and confusing them is what produces a springtime scramble. A founder who understands only the safe harbor tends to underfund the real bill.

There is also a timing subtlety worth understanding. If the big equity event lands in the fourth quarter, a founder can sometimes use the annualized income installment method to show the income arrived late in the year rather than evenly, which can reduce or reshape the required quarterly payments. That method takes careful records of when income was actually recognized, and it is one more reason to have the return preparer involved before year-end rather than after.

Here is a concrete example. Suppose a founder’s prior-year total tax was $8,000, and this year the founder exercises nonqualified options creating $250,000 of ordinary income. Because prior-year income was modest, the safe harbor is 110 percent of $8,000, about $8,800, spread across the four quarters, and paying that keeps the founder free of the underpayment penalty. But the actual tax on $250,000 of ordinary income is far larger, well into six figures at the federal level plus roughly $12,375 to Illinois at 4.95 percent, and that full amount is due at filing regardless of the safe harbor. A founder who set aside only the safe-harbor amount would face a serious shortfall. We calculate the estimates against the founder’s real equity calendar so the payments satisfy the safe harbor and the founder is also holding back enough to pay the genuine tax, coordinating the plan through our tax strategy consulting service. The estimated-tax rules are explained in the IRS estimated taxes guidance, and the Illinois requirements sit with the Illinois Department of Revenue.

The Illinois flat 4.95 percent income tax shapes a Chicago founder individual tax return by making the state calculation predictable and, for large equity events, meaningfully lighter than the graduated systems in California or New York, so a startup CPA can plan around a known state rate rather than a climbing one. Illinois applies the same 4.95 percent rate to all taxable income regardless of amount, and it starts from your federal taxable income, so once the federal return is built the state figure follows in a straightforward way. There is no separate Chicago city income tax on wages or equity, so the city does not add a personal income layer, which is a genuine relief compared with New York City where a local tax rides on top of a high state rate.

The flat rate matters most in a breakout year. When a founder recognizes a large amount of ordinary income from a nonqualified option exercise or from vesting, a graduated state would tax the top dollars at its highest rate, which in California can reach 13.3 percent and in New York City can combine state and city taxes into the high teens. Illinois taxes that same income at 4.95 percent no matter how large it is, so a Chicago founder keeps more of a big equity year than a founder doing the identical transaction in Los Angeles or Manhattan. This is a real structural advantage of being based in Chicago, and it compounds when the amounts are large, because the gap between 4.95 percent and a mid-teens rate widens with every additional dollar of equity income.

The flat rate also interacts well with the two biggest federal equity items. On an incentive stock option exercise, Illinois has no alternative minimum tax, so the federal AMT adjustment does not create a matching state tax, limiting the Illinois consequence of holding ISO shares. On a qualified small business stock sale, Illinois conforms to the federal exclusion through its federal starting point, so a gain excluded under Section 1202 escapes the 4.95 percent Illinois tax as well. In both cases the flat, federally-linked system works in the founder’s favor rather than against it, which is not something a founder in a high-tax coastal state can count on.

One caution belongs in the picture. The flat rate is favorable, but Illinois does add the personal property replacement tax at the entity level, so a founder who runs income through a pass-through such as an S corporation sees roughly 1.5 percent replacement tax on the entity’s income before the flat 4.95 percent applies to what flows to the personal return. That entity-level layer is separate from the individual return but affects the founder’s overall tax, so we look at both together rather than treating the 1040 in isolation.

Here is a concrete comparison. Suppose a founder recognizes $500,000 of ordinary income from a nonqualified option exercise. In Illinois that income is taxed at the flat 4.95 percent, about $24,750 to the state. The same $500,000 recognized by a founder in California could be taxed at a top rate up to 13.3 percent, roughly $66,500 to that state, and in New York City the combined state and city rate could exceed that. The Chicago founder pays less than half the state tax on the identical event purely because of the flat rate and the absence of a city income tax. We prepare the founder return with the Illinois advantage built in and plan the timing of equity events through our tax strategy consulting service. The Illinois rate and filing rules are published by the Illinois Department of Revenue, and the federal return framework sits with the IRS Form 1040 guidance.