Business Tax Preparation

A business tax return is only as good as the books and the owner-level planning behind it. Business tax preparation means filing the right return for your entity, in every state where it is required, and making sure the owners' personal returns match. We prepare returns for sole proprietors, single-member and multi-member LLCs, partnerships, S corporations and C corporations, for businesses in Naperville, Aurora and across Chicagoland and for owners in every state.

What the service includes

• Federal returns. Schedule C with the owner's Form 1040; Form 1065 and Schedules K-1 for partnerships and multi-member LLCs; Form 1120-S and Schedules K-1 for S corporations; Form 1120 for C corporations.
• State returns. For Illinois entities: Form IL-1065, IL-1120-ST for S corporations, and the corporate return for C corporations, as well as returns in other states where the business operates. See multi-state and local tax.
• Owner-level coordination. K-1 amounts flow to the owners' returns, along with basis tracking, estimated payments and the qualified business income deduction.
• Depreciation and asset schedules. Form 4562, including Section 179 and bonus depreciation.
• Information returns. Forms W-2 and 1099-NEC, coordinated with payroll services.
• Extensions. Form 7004 for entities, and Form 4868 for the owners.

Who needs it

Any business with income or expenses, especially one that has changed recently: a new LLC electing S corporation status, a business that added a partner or moved to another state, an owner who started a salary, or a company that began selling across state lines. If you are choosing an entity, read entity selection and our business formation service first.

Dates that matter

For calendar-year entities, the dates follow a fixed rule: the 15th day of the third month for Forms 1065 and 1120-S, and the 15th day of the fourth month for Form 1120.

The 2025 dates are listed in IRS Publication 509 for 2026. The 2026 dates apply the same rules and should be confirmed in the 2027 publication. An extension gives more time to file, not to pay. Late filing by a partnership or S corporation is penalized per owner for each month, so a missed date gets expensive quickly. See the S corporation and partnership late filing penalty.

Illinois specifics

• Replacement tax. Illinois imposes a replacement tax of 1.5% on income of partnerships and S corporations taxable to Illinois, in addition to any federal tax on the owners.
• Pass-through entity (PTE) tax. A partnership or S corporation can elect to pay Illinois income tax at 4.95% at the entity level. The election is made on the entity's return and becomes irrevocable after the extended due date. Electing entities generally make quarterly estimated payments when they expect more than $500 of tax. The owners receive a credit. Whether the election pays off depends on the owners' federal position, so we model it before recommending it.
• Nonresident owners. Illinois requires pass-through withholding for nonresident owners who have not provided Form IL-1000-E, unless the entity elects to pay the PTE tax.

How an engagement works

1. Consultation about the entity, its owners, states of activity and what changed this year.
2. Written engagement agreement covering the returns, scope, deliverables and how fees are determined. We start only after it is signed.
3. Document collection: year-end financial statements or access to the books, bank and loan statements, payroll reports, a fixed asset list, prior-year returns and any ownership changes.
4. Preparation. We reconcile the books to the return and prepare the federal and state forms and K-1s.
5. Review and delivery, including the owners' tax effects, before filing.
6. Follow-up: estimated payments for next year and coordination with the owners' personal returns.

Common problems we fix

• Books that do not tie to the return. Owner draws recorded as expenses, loans recorded as income, and personal charges mixed into business accounts. Our bookkeeping service cleans those up.
• S corporations with no payroll. An owner who works in the business generally needs reasonable pay through payroll. See reasonable compensation.
• Missing elections. A late Form 2553 or an overlooked depreciation election can usually be fixed, but sooner is easier.
• Equipment purchases handled by default. For qualified property acquired after January 19, 2025, 100% first-year depreciation is available, and the 2025 Section 179 limit is $2,500,000. We choose between them deliberately, because the answer can affect state returns and later years.
• Information returns filed late or not at all. See Form 1099-NEC and 1099-K.

How we can help

We prepare the entity and owner returns together so the numbers agree, and if you are weighing a different structure, we can compare outcomes before you file. We also support businesses with accounting and financial statements. Corporations that file 10 or more returns of all types in a year must e-file their income tax returns, and we handle that for you. We serve businesses in Naperville, Aurora and all of Chicagoland, and we work with business owners in every state, in person or remotely. Contact us to begin.

Frequently asked questions

General information only, not tax, legal or accounting advice for your situation. Rules, limits and deadlines change; confirm the current rules with the official source or a qualified professional before you act. Reading this page does not create a professional relationship with CPA Tax Payroll and Accounting Corp.