Business tax returns are the most authoritative financial document in any acquisition because they represent what the seller certified to the IRS as accurate. Learning to read and analyze business tax returns is one of the most valuable skills any Illinois business buyer can develop.
What Entity Returns Tell You
S-corporation returns (Form 1120S) show business revenue, expense categories, and officer compensation on Schedule K. Partnership returns (Form 1065) show similar information plus partner distributions. C-corporation returns (Form 1120) show corporate taxable income after officer salaries. Schedule C filers (sole proprietors) show all income and expense on their personal return. In each case, look at the revenue trend across three years, the consistency of major expense categories as a percentage of revenue, and the reported net income that forms the base for SDE calculation.
Key Line Items to Analyze
Focus on: gross revenue or sales (Line 1 of most business returns), cost of goods sold or cost of services, officer or owner compensation (Schedule E of 1120S, Line 17 of 1120), depreciation and amortization, interest expense, and net ordinary business income. Expenses that are unusually high or unusually low relative to revenue deserve explanation. Year-over-year changes of more than 15–20% in any major category warrant investigation.
Personal tax returns cross-validate business returns for pass-through entities. A sole proprietor's Schedule C net income should flow through to their Form 1040. An S-corp shareholder's K-1 income should appear on their personal return. Discrepancies between business returns and personal returns are red flags that require explanation before you proceed.
Recast Seller’s Discretionary Earnings, then apply a planning multiple for this Illinois business. Replacement labor is subtracted. This is a planning tool, not an appraisal.
Before debt, working-capital peg, holdback, and tax. Educational only.
What this Illinois guide is for
How to Review Tax Returns for a Business Purchase is a working answer for owners and buyers. We will not invent a statewide average sale price. We will show the earnings math, the Illinois clocks that delay a close, and the questions a serious counterparty will ask.
Marketplace context from BizBuySell’s Q2 2026 Insight Report (median reported sale $349,250, 2.7× cash-flow multiple, 14% of owners with a professional valuation) is context — not your quote.
Illinois diligence that is not optional
Three years of tax returns, bank statements that match the P&L, the lease, licenses, customer concentration, and any environmental file belong in the first data room. See the buy-side checklist.
Documents to gather this week
- Three years of signed business tax returns and matching P&Ls
- Year-to-date P&L, balance sheet, and three months of bank statements
- Current lease, amendments, and a plain-English remaining term
- License and permit list, including who holds each card
- Top-customer concentration (names redacted until an NDA)
A simple Illinois close calendar
Plan six to twelve months from cleanup to close on a prepared Main Street deal. Start CBS-1 and any Chicago or Cook notices at letter-of-intent, not the week of funding. Landlord consent often takes longer than the lender.
Related pages on this site
Educational only — not legal, tax, or a formal appraisal. Confirm bulk-sale notices, licenses, and tax allocation with counsel and a CPA.
Questions
No. This is education and planning math. A professional opinion of value is a confidential conversation. We work on a success fee if you engage a sale process. There is no file-upload portal.
Start with adjusted seller’s discretionary earnings, then a vertical planning band. A marketplace average is context, not your quote.
Personal professional licenses do not transfer. Municipal registrations and state notices have their own calendars. Confirm the path before you grant exclusivity.
Most prepared Main Street sales take about six to twelve months from cleanup to close. License transfers, landlord consent, and SBA underwriting add weeks.
CBS-1 is the Illinois bulk-sale notice. File it at least ten business days before an asset transfer that meets the statute. Late filing can put Illinois tax risk on the buyer.