In 2018, thousands of Indiana taxpayers missed millions of dollars in refunds because they filed late, incorrectly, or didn’t file. A missed deadline or an incomplete return doesn’t just postpone your refund—it can lead to costly penalties, interest charges, and added stress. Filing your return correctly and on time protects your income and ensures you claim every dollar you are entitled to.
This step-by-step guide on how to file your Indiana tax return for 2018 is built for individuals, small business owners, and independent contractors who want clarity and confidence in the filing process. Whether you lived in Indiana for the whole year, moved in or out during 2018, or earned income from Indiana sources while living elsewhere, we’ll explain exactly which state tax forms to use, how your federal return fits into the process, and which deductions and credits may apply to your situation.
Filing early has essential advantages: faster refunds, reduced identity theft risk, and more time to address issues if your return is rejected. Choosing to e-file can cut refund wait times to around 30 days, compared to the painfully slow paper process that can take eight weeks or more. By following this guide, you’ll know which documents to prepare, where and when to submit your return, and how to track your refund through the Indiana Department of Revenue’s secure system—helping you avoid costly mistakes, claim eligible benefits, and keep more money.
Knowing whether you must file is the first step in avoiding penalties and securing your refund. In 2018, Indiana’s filing rules were clear: if you lived in Indiana or earned income from Indiana sources, you were likely required to file a state return.
Full-Year Indiana Residents must file if any of the following apply:
Part-Year Residents are those who moved to or from Indiana during 2018. They must file if they had any Indiana-source income while living in the state. This could include wages earned from an Indiana employer, rental income from property in the state, or income from operating a business within Indiana.
Nonresidents must also file if they earned income from Indiana sources in 2018. Examples include working temporarily in Indiana, running a business with Indiana operations, or receiving income from an Indiana-based rental property.
Special rules apply for residents of reciprocal states—Kentucky, Michigan, Ohio, Pennsylvania, and Wisconsin. If you lived in one of these states but worked in Indiana, you may file Form IT-40RNR instead of a standard return, ensuring you are taxed only by your home state. Even if you are not technically required to file, doing so can be financially beneficial. Many people file voluntarily to claim refunds for withheld taxes, credits, or deductions they qualify for.
The due date for filing your 2018 Indiana tax return was April 15, 2019. This aligned with the federal filing deadline, which meant that anyone required to file a federal return generally had the exact date for their state filing. Missing this date could lead to late filing penalties of up to 10% of the tax owed and monthly late payment penalties of 5% until the balance is paid.
If you needed more time to file, you could request an extension in one of two ways:
For 2018 returns, the extended deadline was November 14, 2019. However, it is essential to note that an extension to the file is not an extension to pay. To avoid penalties and interest, at least 90% of your expected state tax liability must be paid by April 15, 2019. This payment could be made online, by mail, or through an approved third-party service.
Filing well before the deadline helps you avoid the last-minute rush that can cause costly errors, such as entering the wrong form information or forgetting to include required schedules. It also reduces the risk of rejected returns due to small mistakes, giving you time to correct them without missing the final date. For many taxpayers, the safest approach is to prepare and submit both your state and federal returns simultaneously.
The 2018 tax year included several significant updates that could affect how you file your Indiana state tax return. These changes came primarily from federal tax reform and had varying impacts on state calculations.
Filing your 2018 Indiana tax return starts with selecting the correct state tax forms and attaching the schedules that match your filing status and income sources. Using the wrong form or missing a required schedule can delay your refund or result in penalties.
When filing Form IT-40, you must attach:
When filing Form IT-40PNR, you must attach:
Attach these only if applicable:
Always check the instructions for each form and verify you are using the correct year’s version. Forms and schedules can be downloaded from the Indiana Department of Revenue’s site. Submitting incomplete or incorrect paperwork is one of the most common reasons a return is delayed or rejected.
Following a structured process ensures your Indiana state tax return is complete, accurate, and submitted on time. Use this step-by-step approach to avoid costly mistakes and get your refund faster.
Before you start, collect all essential records. Missing paperwork is one of the main reasons a return gets rejected or delayed.
Indiana starts its calculations with your federal adjusted gross income (AGI).
Choose the correct form based on your residency status: IT-40, IT-40PNR, or IT-40RNR.
Attach all schedules required for your specific form.
Carefully verify:
You can file a tax return electronically or by mail:
Maintain a full copy of your return, supporting documents, and proof of payment for at least four years. This helps if the Indiana Department of Revenue requests more details later or if you need to prepare future returns. Filing early and electronically speeds up your refund, reduces identity theft risk, and allows more time to fix issues before the due date.
Once your 2018 Indiana state tax return is complete and reviewed, the final step is choosing how to submit it. Selecting the proper method can affect processing times, potential fees, and how quickly you receive your refund.
If you prefer to file a paper return, use the correct address based on whether you owe payment or expect a refund.
With Payment:
Indiana Department of Revenue
P.O. Box 7224
Indianapolis, IN 46207-7224
Without Payment:
Indiana Department of Revenue
P.O. Box 40
Indianapolis, IN 46206-0040
When mailing:
Submitting early and through online methods helps avoid processing delays, reduces errors, and ensures you receive your money as quickly as possible.
If your 2018 Indiana state tax return shows you owe money, you have several ways to pay securely. Making your payment on time avoids extra fees and penalty charges, which can significantly add to your total cost if unpaid.
If your state return results in a refund, you can track it through the Indiana Department of Revenue’s “Where’s My Refund” tool.
Before submitting your 2018 Indiana state tax return, use this checklist to ensure everything is accurate, complete, and ready for processing. A careful review can help you avoid costly penalty charges and delayed refunds.
Completing this checklist before you submit your state return helps you determine that all information is correct, ensures compliance, and maximizes the benefits you’re entitled to claim.
You can download official Indiana state tax forms for 2018 from the Indiana Department of Revenue website. Always choose forms for the correct year, as outdated versions can delay your state return. Each form is specific to the type of filer and subject to annual changes, so review the instructions carefully before completing and submitting your paperwork.
Filing your federal tax return does not automatically complete your Indiana state return. Indiana requires its filing using the proper Indiana state tax forms. Your federal return information is a starting point, but the state has rules and requirements subject to Indiana tax law.
If you moved into or out of Indiana during 2018, you may need to file a tax return as a part-year resident. Use the correct Indiana state tax forms for part-year filers, and report only the income subject to Indiana tax. Keep detailed records of when you lived in Indiana to determine how much of your income is taxable at the state level.
State tax applies to all taxable income subject to Indiana law, while county tax rates vary depending on your county of residence as of January 1, 2018. The Indiana state tax forms include separate sections for calculating each. Both taxes are paid together when you file your state return; the total will determine your final balance due or refund.
Failing to file your state return by the deadline can result in penalties and interest. The Indiana state tax forms clearly outline these charges, which are subject to change yearly. Common penalties include a 10% failure-to-file fee and a 5% monthly failure-to-pay fee. Filing on time helps you avoid these costs and ensures you receive any refund you’re owed faster.
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