Hawkeye Trophy & Engraving has seventeen Iowa dates in 2026, and none of them is the fifteenth

The moment

Hawkeye Trophy & Engraving is a trophy, plaque and engraving shop in Marshalltown, Iowa. Lou Brandt opened it in 2011 and now sells school awards, league plaques and retirement gifts. It has two W-2 employees besides Lou and is taxed as an S corporation. Iowa sales tax is collected on most of what goes over the counter. It is the first day of October and Lou is laying out next year's tax sheet.

What they did instead

Lou's habit was the last day of the month. Sales tax, last day, every month, written on a wall calendar. In 2025 he was right about most of them. He was wrong about the ones that fall on a Saturday or Sunday, and he did not find out that Iowa moves them to the following Monday until a bookkeeper pointed it out. The estimated payments were the bigger muddle. He had the federal dates in his head, April 15 and June 15, and assumed Iowa's matched. They do not. Nobody had put the Iowa dates, the federal dates and the payroll dates on one sheet.

The questions a CFO asks first

1. How many Iowa dates does the shop have, and how many of them are not the last day of a month?
2. What does the year look like if Iowa has the shop file once a year instead of monthly?
3. When is the fourth estimated payment, and why is it not January 31?
4. What would a calendar-year C corporation pay Iowa that an S corporation does not, and which Iowa dates would it not have?

The arithmetic, shown

Five scenarios, all through the tool's own engine, all built on Hawkeye's profile: an S corporation, two W-2 employees, no 1099 contractors, Iowa as the state, registered to collect Iowa sales tax.

Scenario one: monthly, the schedule the shop is on. Iowa puts a business on the monthly schedule at $1,200 or more of sales and use tax a year. The Department's page reads

> Monthly: $1,200 or more in sales and use tax per year. Due on or before the last day of the following month.

Hawkeye collected $3,600 last year, $300 a month, so it is well over the line. Iowa publishes a rule, not a table of dates, so the tool works each date out. The tool returns twenty-seven dated line items. Seventeen are Iowa: thirteen sales-tax returns and four individual estimated payments. The other ten are federal payroll and federal estimated-tax lines. The weekend rule is on the Department's page:

> If the due date falls on a Saturday, Sunday, or holiday as defined in Iowa code 421.9A, then the due date is the following day that is not a Saturday, Sunday, or holiday.

Five of the thirteen returns are not the last day of a month. January 31, 2026 is a Saturday, February 28 is a Saturday, May 31 is a Sunday, October 31 is a Saturday and January 31, 2027 is a Sunday. The tool dates them

> 2026-02-02

> 2026-03-02

> 2026-06-01

> 2026-11-02

and

> 2027-02-01

All five are Mondays. The other eight fall on a weekday and stay on the last day of the month. The tool says how it got there:

> Iowa publishes these as rules (the last day of a month) rather than a dated table, so this tool worked out each date and moved any that fall on a Saturday or Sunday to the next business day, as the Department's pages say.

The owner's estimates are on their own schedule:

> Installment 1 – April 30. Installment 2 – June 30. Installment 3 – September 30. Installment 4 – January 31.

Those are not the federal months. The tool dates the first three as April 30, June 30 and September 30, all weekdays. The fourth is January 31, 2027, a Sunday, so it moves to the same Monday as the January return, February 1, 2027. That day carries two Iowa payments. February 2, 2026 is heavier still, with four items: the fourth-quarter Form 941, Form 940, the W-2s and the Iowa January return. April 30 carries three, the first-quarter Form 941, Iowa's first estimate and Iowa's March return. The tool is also explicit about what it has not asked:

> This tool doesn't ask whether an Iowa estimated payment is actually owed (the Department's threshold is $1,000 of tax for 2026), so it shows the schedule that would apply if one is.

Scenario two: annual. Suppose Iowa had assigned the shop to the lower schedule. The Department's page reads

> Annually: less than $1,200 in sales and use tax a year. Return and payment due on or before January 31 following each calendar year.

The tool returns fifteen items, not twenty-seven. Twelve fewer, one Iowa return in place of thirteen. January 31, 2027 is a Sunday, so the single return is dated

> 2027-02-01

and lands on the same day as the fourth estimate.

Scenario two (b): a schedule the tool does not date. The tool returns fourteen items and no Iowa sales-tax date at all. The federal lines and the four Iowa estimates are still there. The tool names the gap:

> Seasonal filers have their own pattern

and sends the owner to the Iowa Department's page and the GovConnectIowa account for the schedule Iowa actually assigned.

Scenario three: the frequency not yet confirmed. With everything else answered and the filing frequency left blank, the tool does not guess. It returns a named refusal: missing: ["how often Iowa has this business file sales tax"]. Nothing computes until there is an answer.

Scenario four: the identical profile as a calendar-year C corporation. The tool returns twenty-eight items, not twenty-seven. The individual schedule goes. Federal Form 1120 and four Form 1120-W deposits arrive, along with four Iowa corporate estimates. The Department's rule for business entities is

> the last day of the fourth month following the beginning of the tax year; the last day of the sixth month; the last day of the ninth month; the last day of the twelfth month.

For a calendar year that is April 30, June 30, September 30 and December 31. The last is dated

> 2026-12-31

a month before the S corporation's January 31 estimate, which waits until February 1, 2027. Iowa has seventeen dates for either entity type. The difference is when the fourth estimate falls, and there is no Iowa return date for the corporation. The tool says so:

> Iowa's C corporation annual return date isn't computed: no Department page this run could read states it, so check tax.iowa.gov directly.

Scenario four (b): the same corporation, tax year unconfirmed. Mark the corporation's tax year as not calendar-year, or as unconfirmed, and the tool returns nineteen items. Nine dates disappear: four Iowa estimates and five federal (Form 1120 and the four 1120-W deposits). The thirteen sales-tax returns stay. The tool gives the reason:

> This tool only computes Iowa corporate dates for a calendar-year C corporation (tax year January-December). This corporation's tax year isn't calendar-year, or isn't confirmed as one, so no Iowa corporate date is computed here; the Department's rule counts months from the start of the tax year, so check tax.iowa.gov directly.

What changed

Lou has thirteen return dates on the same sheet as his estimates and payroll dates. The "last day of the month" on the wall calendar is thirteen dated lines, five of them Mondays. The fourth estimate has a date, February 1, not the January 31 he would have written. The number to watch is the filing frequency. Thirteen dates or one is Iowa's assignment, set at $1,200 of tax a year, and it changes the size of the sheet by more than any other single answer.

What the tool will not do

It will not decide which schedule the shop is on. Iowa assigns it, so the tool asks and builds dates from the answer. It will not compute the tax owed on any return or payment. It covers the base dates and leaves out a lot that the Department also has:

> This tool doesn't cover Iowa withholding, pass-through returns (S corporation and partnership), pass-through entity tax, the C corporation annual return, seasonal sales-tax filers, or local option sales tax.

That list matters for Hawkeye specifically. It is an S corporation, so the pass-through return and any pass-through entity tax are off the sheet, and so is Iowa withholding on the two employees' wages. The tool does not ask whether an estimated payment is owed at all. The Department's own threshold is $1,000 of tax for 2026, and the shop may owe none. The rule also moves a date that falls on an Iowa state holiday. The tool's note says each date was checked by hand for that and none lands on one, but it has no holiday calendar of its own. The tool will not know about an extension, a payment plan or a penalty already assessed on any date above. This tool supports a named list of states, which the state picker in the tool shows, and every line above is the plain due date for the entity type it was told about.