Chicago Tax Filing Playbook: Deadlines, Fees, and CPA Tips to Avoid Costly Mistakes

As the March tax filing rush approaches, many Chicago taxpayers are focused on one thing: filing accurately and on time without creating problems later. Whether you are finalizing a straightforward return or managing more complex income, understanding Illinois deadlines, common filing mistakes, and how CPA oversight reduces risk can make a meaningful difference.

This Chicago tax filing playbook walks through what filers need to know before the deadline, including key 2026 dates, extension rules, fee red flags, and when working with a CPA becomes especially important.

If you are still deciding whether professional help is necessary, start with Do I Need a CPA for My Taxes? and then come back to this playbook once you know which filing path fits your situation.

Step 1: Know the Key Chicago and Illinois Tax Deadlines

For most individual filers, the federal and Illinois income tax filing deadline is April 15, 2026. If April 15 falls on a weekend or holiday, the deadline may shift slightly, but the obligation remains the same.

Important reminders for Illinois taxpayers:

• Illinois generally follows the federal filing deadline

• State returns are filed separately from federal returns

• Payment deadlines are not automatically extended just because you request more time to file

Missing deadlines can trigger penalties and interest, even if you ultimately owe a relatively small amount. If you want a clear, step-by-step walkthrough of what we collect and how we prepare returns, see Tax Preparation & Planning Services.

Step 2: Extensions Give You Time to File, Not Time to Pay

A common misconception among Chicago filers is that filing an extension delays payment. It does not.

An extension:

• Gives you additional time to file paperwork

• Does not extend the deadline to pay taxes owed

If you expect to owe, an estimated payment should be made by the original deadline to reduce penalties and interest. Many penalties arise not from underreporting income, but from misunderstanding extension rules.

This is also one reason filers who used DIY software in prior years sometimes switch to professional preparation. If you are comparing your options, CPA vs TurboTax explains the practical differences in responsibility, documentation, and risk.

Step 3: Understand Common CPA Fees and Red Flags

Tax preparation fees in Chicago vary based on complexity, not just income level.

Factors that typically increase fees include:

• Self-employment or 1099 income

• LLC or S-Corporation ownership

• Rental or investment activity

• Multi-state filing

• Prior-year issues or IRS correspondence

If you want realistic fee ranges and what drives pricing, review How Much Does a CPA Charge for Tax Preparation? before selecting a preparer based on price alone.

Fee red flags to watch for

• Refund-based pricing: Charging a percentage of your refund is prohibited for many credentialed preparers and is a major quality warning sign

• No PTIN disclosure: Every paid tax preparer must have a valid Preparer Tax Identification Number

• Lack of engagement clarity: You should understand what services are included before work begins

Transparent pricing and proper credentials are signs of a compliant, professional practice.

Step 4: A Plain-English Explanation of the $600 Rule

The “$600 rule” is commonly used to refer to information reporting rules that require certain businesses and platforms to issue forms such as 1099-NEC or 1099-K once payments meet specific thresholds.

What this means for taxpayers:

• Receiving a 1099 does not automatically mean your situation changed overnight

• Income was already taxable even before the form was issued

• IRS matching has increased, so omitted income is more likely to trigger a notice

Many notices result from income being reported to the IRS but not reported on the return. CPA review helps ensure reported income aligns with IRS information returns.

Step 5: How CPA Oversight Reduces Audit and Notice Risk

While audits are relatively rare, IRS notices are common. Most notices arise from:

• Mismatched income reporting

• Missing forms

• Mathematical errors

• Unsupported deductions

A CPA’s role is to reduce these risks by:

• Verifying income against available information reporting

• Reviewing deduction support and documentation

• Applying current tax law correctly

• Ensuring consistency across federal and Illinois filings

If you want this level of oversight as part of a complete, compliant filing process, this is exactly what we provide through Tax Preparation & Planning Services.

Step 6: Multi-State and Nonresident Filing Considerations

Chicago filers frequently encounter multi-state issues due to:

• Remote work in another state

• Business income sourced outside Illinois

• Rental or investment property in another state

Nonresident and part-year resident filings require careful allocation of income. Errors in state sourcing are a common trigger for notices and assessments. This is an area where professional oversight is particularly valuable, especially when you have ongoing business activity across state lines.

If you are a business owner and your books are not fully tax-ready, multi-state filing often becomes much harder. In those cases, pairing filing with clean, accurate records through Bookkeeping & Accounting Services can reduce errors and streamline the process.

Step 7: Security, Standards, and Professional Responsibility

When working with a CPA firm, professional standards matter. At Hyman

Financial Solutions, tax preparation follows:

• AICPA professional standards

• IRS Circular 230 requirements

• Secure portal protocols for document exchange and document retention

If you want to see how we handle secure document collection and client communication, you can review our approach through Hyman Financial Solutions and submit documents through the portal linked there.

Final Filing Checklist Before the March Rush

Before finalizing your return, confirm that you have:

• All W-2s and 1099s

• Mortgage interest and property tax statements

• Investment and retirement income forms

• Business income and expense summaries if applicable

• Prior-year returns available for reference

Early preparation reduces last-minute stress and increases accuracy.

Final Thoughts

Filing taxes in Chicago is not just about meeting a deadline. It is about filing correctly, paying what is required, and avoiding problems that surface months later. Understanding deadlines, fee structures, and compliance risks helps taxpayers make informed decisions before the March rush intensifies.

For taxpayers with business income, multiple states, or changing circumstances, CPA oversight provides clarity and confidence that filing decisions align with current rules.

Next Steps

If you are finalizing your return and want professional oversight for accurate, on-time filing, schedule tax preparation early through Tax Preparation & Planning Services. If your situation is evolving, ask about year-round planning so future filings are easier and more predictable through Small Business Tax & Advisory Services.