IL-505-I

This article explains what Illinois Form IL-505-I is, who must file it, how and when to file and pay, and how to complete every line and field on the payment voucher and its Tax Payment Worksheet to make a timely automatic extension payment for Form IL‑1040 without confusion or missed steps.

Form IL-505-I, Automatic Extension Payment for Individuals, is Illinois’ payment voucher used by individual taxpayers who cannot file Form IL‑1040 by the original due date but expect to owe tax; it lets you calculate and remit your tentative Illinois income tax and other taxes reportable on Form IL‑1040 by the original due date so you avoid late-payment penalties and interest during the automatic six‑month filing extension window. Illinois automatically grants a six‑month extension to file (to October 15 for calendar-year filers), but this does not extend time to pay; if you will owe, you must pay by the original due date, and IL‑505‑I is only required when you are paying by paper check or money order instead of electronic options. Do not file IL‑505‑I if your worksheet shows no tentative tax due or you choose to pay electronically by card, EFT, or bank account debit, and remember to claim any IL‑505‑I payment on your IL‑1040 (Line 26) when you later file.

Who Must File

  • File IL‑505‑I if all are true: you cannot file IL‑1040 by the original due date, you will owe tentative tax per the Tax Payment Worksheet, and you are paying by paper check or money order rather than electronically.
  • Do not file IL‑505‑I if you owe nothing on the worksheet or you pay the extension amount electronically via credit card, EFT, or bank account debit.

Extensions And Deadlines

  • Automatic Illinois six‑month filing extension is granted to all individuals; calendar-year filers have until October 15 to file, but payment of any tentative tax is still due by the original due date to avoid late‑payment penalties and interest.
  • Additional extension beyond six months is allowed only if the IRS grants a longer federal extension; attach a copy of the federal extension approval to your IL‑1040 if you file after the Illinois automatic period.

When And Where To File And Pay

  • File and pay by the original due date of the annual return (or as soon as you realize you owe tentative tax) if you will owe and are sending a paper check or money order with IL‑505‑I.
  • Mail the voucher with payment to: Illinois Department of Revenue, P.O. Box 19005, Springfield, Illinois 62794‑9005; make checks payable to “Illinois Department of Revenue,” and write your Social Security number, tax year, and “IL505I” on the check or money order.

How To Pay Electronically

  • Online: Use MyTax Illinois at mytax.illinois.gov to pay from checking or savings (requires your IL‑PIN).
  • Credit card: Pay by MasterCard, Discover, American Express, or Visa via approved vendors (a convenience fee applies); vendor options include ACI Payments, payILtax, and Link2Gov/FIS with web and phone channels listed on the form.
  • Electronic options provide immediate confirmation and avoid mail delays; do not mail IL‑505‑I if you pay electronically.

Penalties, Interest, And Attachments

  • Penalties include late‑filing if you miss the extended due date, late‑payment if you do not pay by the original due date, and bad check if your payment is dishonored; interest accrues from the day after the original due date until paid, and the Department will bill penalties and interest.
  • If you file within the automatic six‑month period, do not attach an explanation; if you file after six months with an IRS‑approved longer extension, attach the federal extension document to avoid late‑filing penalty.
How to Complete Tax Payment Worksheet

How to Complete Tax Payment Worksheet

Use this worksheet to determine your tentative tax due; round to whole dollars on Line 7 and on the voucher.

  • Line 1 — Income tax and other taxes: Enter the total individual income tax you expect to owe and any other taxes reportable on Form IL‑1040; use IL‑1040 as a worksheet by completing Lines 1–14 to estimate income tax and Lines 20–22 for other taxes, then add them here.
  • Line 2 — Withholding and pass‑through withholding: Enter Illinois income tax withheld from wages or other income and any pass‑through withholding reported to you on Schedule K‑1‑P or K‑1‑T for the year.
  • Line 3 — Estimated income tax payments: Enter total Illinois estimated payments made with Form IL‑1040‑ES for the year, including any prior‑year overpayment credited to this year.
  • Line 4 — Previous Form IL‑505‑I payment: Enter any Illinois income tax paid earlier for this tax year with a prior IL‑505‑I submission.
  • Line 5 — Estimated allowable credits: Enter estimated allowable credits, including credit for tax paid to other states (Schedule CR), Illinois Property Tax paid, education expenses, volunteer emergency worker, Illinois Earned Income Tax Credit and Child Tax components (Schedule IL‑EEITC), pass‑through entity tax credit, and credits from Schedule 1299‑C; follow the schedules’ instructions.
  • Line 6 — Total tax payments and credits: Add Lines 2 through 5 and enter the total.
  • Line 7 — Tentative tax due: Subtract Line 6 from Line 1; round to whole dollars and enter on Line 7 and on the IL‑505‑I voucher; if Line 7 is at least 1, you must pay that amount now, and if it is less than 1, do not file the form and no payment is due.

How to Complete IL‑505‑I Payment Voucher

Complete the detachable bottom voucher only if you are paying by check or money order; return only the voucher portion with your payment and keep the rest for your records.

  • Tax year: For calendar year filers, confirm “For calendar year ending 12/24”; for fiscal‑year filers, enter the fiscal year ending month and year in the space provided.
  • Tentative tax due: Enter the whole‑dollar amount from Worksheet Line 7 as your extension payment amount.
  • Your Social Security number: Enter your SSN exactly as on your federal return in the first SSN box.
  • Spouse’s Social Security number: Enter spouse’s SSN in the second box if filing jointly; leave blank if not applicable.
  • Your first name and initial: Enter your first name and middle initial as shown on your federal return.
  • Spouse’s first name and initial: Enter spouse’s first name and middle initial if applicable.
  • Your last name: Enter your last name; for joint filers, use the primary taxpayer’s last name matching the federal return.
  • Street address: Enter your complete mailing street address.
  • City: Enter your city.
  • State: Enter your two‑letter state abbreviation.
  • ZIP: Enter your 5‑digit ZIP code (and 4‑digit extension if used by your postal standard).
  • Daytime phone number: Enter a daytime phone number for contact regarding payment processing if needed.
  • Check or money order: Make payable to “Illinois Department of Revenue”; write your SSN, tax year, and “IL505I” on the memo line; do not staple or attach the check to the voucher in a way that obscures any fields.
  • Mailing address on voucher: Mail to “ILLINOIS DEPARTMENT OF REVENUE, PO BOX 19005, SPRINGFIELD IL 62794‑9005” as printed; use the preprinted address exactly to ensure proper routing.
  • Official use section: Leave the “Official Use” area blank; it is for Department processing only.

Important Filing Notes

  • Only return the bottom voucher with your payment; do not file the form if no payment is due or if you pay electronically or by credit card.
  • Do not redact Social Security numbers on the voucher, as redaction can cause processing delays.
  • Save a copy of the worksheet and your payment confirmation; later, report the IL‑505‑I payment on IL‑1040, Line 26, to receive proper credit.
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