Business Tax Returns and Planning for Illinois Small Businesses

Business tax returns and planning work best when the two are done together: the return reports what already happened, and the planning decides what the next year looks like. Our Aurora, Illinois firm prepares federal and Illinois business returns for sole proprietors, partnerships, LLCs, S corporations and C corporations, and for businesses that have a parent, affiliate or investor in Canada or India. The U.S. side is ours; Canadian and Indian company filings stay with your Canadian CPA or Indian CA, and we coordinate so the numbers match.

Who needs business tax returns and planning?

• Owners of an LLC, S corporation or C corporation in Aurora, Naperville, Geneva or Joliet.
• Consultants and freelancers who are outgrowing a sole proprietorship.
• Founders from India or Canada who have set up a U.S. company or LLC.
• U.S. owners of a Canadian corporation or an Indian private limited company or LLP.
• Anyone buying or selling a business who needs the tax consequences mapped first.

Which return does each entity file?

The IRS says your form of business determines which income tax return you file. Most small businesses fall into one of these patterns.

An extension on Form 7004 generally must be filed by the regular due date. Illinois taxes corporations at 7% plus a 2.5% replacement tax, and partnerships, trusts and S corporations at a 1.5% replacement tax, according to the Illinois Department of Revenue. Illinois also has its own returns for each type of entity.

An S corporation cannot have a nonresident alien as a shareholder, which matters for founders who are not yet U.S. residents. Our guide to U.S. entity types and tax forms goes deeper, and the Illinois income tax guide explains the state side.

Cross-border business filings

For Canadian corporations the federal rate after the general reduction is 15%, and 9% for a Canadian-controlled private corporation claiming the small business deduction, before provincial tax. For Indian domestic companies the rates for assessment year 2026-27 were 22% under the concessional regime, 25% or 30% otherwise, plus surcharge and cess. India's Income-tax Act, 2025 took over from the 1961 Act on April 1, 2026, so your CA confirms the current rules. See our guides to the T2 corporation return and Indian private limited company compliance, and the three-country corporate tax comparison.

How the engagement works

1. Consultation. We review your entity, owners, states, payroll and any foreign connections.
2. Written engagement agreement. It lists each return, the planning work and the fee basis, and you sign it before we begin.
3. Document checklist. You receive a list matched to your entity type.
4. Preparation. We prepare books-to-tax adjustments, depreciation, owner basis and the Illinois return.
5. Review. You see a summary and the owner-level impact, and we resolve open questions.
6. Filing. We e-file, send K-1s to owners and give you the filed copies.
7. Follow-up. We calendar estimated taxes, set a mid-year planning meeting and answer notice questions.

What planning covers

• Entity choice and conversions. Moving from a sole proprietorship to an LLC taxed as an S corporation, or the reverse, has payroll, state and basis consequences. Liability protection differs by structure too, so we flag that for your attorney.
• Owner pay. S corporation owners who work in the business generally need to run payroll, which links to our payroll service.
• Retirement plans. For 2026 the 401(k) employee deferral limit is $24,500 and the overall annual additions limit is $72,000, per the IRS; a plan can shift income into later years.
• Estimated taxes. Individuals who expect to owe $1,000 or more generally pay in installments.
• Equipment and timing. We model purchases and income timing before year-end.
• Foreign affiliates. Transfer pricing, loans, royalties and management fees between a U.S. company and a Canadian or Indian affiliate need written agreements and consistent reporting.

Documents to prepare

• Prior-year returns and the current-year trial balance or financial statements.
• Bank, credit card and loan statements, and fixed-asset purchase invoices.
• Payroll reports (Forms 941 and W-2 totals) and 1099 contractor payments.
• Ownership records: operating agreement, stock ledger, capital contributions and distributions.
• For foreign owners or affiliates: related-party transactions, foreign entity documents and a list of foreign bank accounts.

Common situations and fixes

• The LLC never made an S election but the owner thought it had. We review whether a late-election relief request fits.
• No Form 5472 for a foreign-owned LLC. Missing the form is a known penalty trap, and we address it as soon as it is found. See the Forms 5472 and 1120 guide.
• Personal and business expenses mixed. We reclassify and set up a clean system with our bookkeeping service.
• Illinois registrations missing. We check the sales-tax, withholding and unemployment accounts.

A worked example

A design studio in Batavia is an LLC with two members, one living in Illinois and one living in Mississauga. It is taxed as a partnership with $180,000 of net profit split equally. The partnership files Form 1065 and Illinois's partnership return, and each member gets a Schedule K-1. Because one partner is not a U.S. person, the partnership must also handle special withholding and reporting for that partner's share. The Mississauga partner's Canadian CPA reports the same income on a T1 return and claims a credit for U.S. tax paid. Every number reconciles to the same K-1, which is why we sit between the two sets of filings.

How we can help

We prepare and plan business returns from our Aurora, Illinois office for clients across Kane, DuPage, Will and Kendall counties. We handle the U.S. side and coordinate with your Canadian CPA or Indian CA so all three filings agree. For startups and equity-based pay, see startup and equity tax planning, and for the broader picture see cross-border tax services. Our full list of services is on the services page.

Frequently asked questions

General information only. It is not tax, legal, accounting or immigration advice for your situation, and rules change; confirm the current rules with the official source or a licensed professional in the relevant country.