Tippecanoe Pool & Spa files Indiana sales tax on the 30th, and $100 more a month of average tax would move it to the 20th

The moment

Tippecanoe Pool & Spa is a pool and spa retailer in Lafayette, Indiana. Marguerite Halloran and her brother Owen bought it from the founder in 2019. The shop sells chemicals, pumps, covers and hot tubs, and services what it sells. It has one W-2 employee through the winter and more in summer, and it is taxed as an S corporation. Indiana sales tax is collected on the counter sales and the equipment. In the twelve months ending June 30, 2025, the shop collected $10,800 of sales tax, and in the twelve months ending June 30, 2026 it collected $13,200. It is the last week of September, and Marguerite is putting next year's tax dates on one sheet, as she does every fall.

What they did instead

Marguerite kept a calendar entry that said "sales tax, the 30th." It worked in every month but one. February has no 30th, and she never knew whether January's return belonged at the end of February or in March. Most years she filed it in the last week of February to be safe and paid a bookkeeper for an hour to confirm that this was early, not late. She also had no way to see that two of the shop's 30ths land on a weekend, or that one of the busiest weeks of the year already carries three payroll filings before a sales-tax return is counted. The cost was not a penalty. It was an hour of paid time a year, and a return filed a few days before it needed to be.

The questions a CFO asks first

1. What is the shop's average monthly sales tax, and which side of Indiana's $1,000 line does it fall on?
2. On which dates in 2026 is each monthly return due, and which of them move because the 30th is a weekend?
3. What happens to the year if the shop is moved to the 20th schedule?
4. Does the shop's entity type change any of this?

The arithmetic, shown

Four runs, all through the tool's own engine, all built on Tippecanoe's profile: an S corporation, one W-2 employee, no 1099 contractors, Indiana as the state, registered to collect Indiana sales tax.

The test, before the tool. Indiana's Department of Revenue sorts monthly filers by last year's average:

> Early Filers for sales tax and companion taxes are defined as those having $1,000 or greater average monthly tax liability for the prior fiscal year ending on June 30 of the previous calendar year.

The shop's year to June 30, 2025 was $10,800 of tax. Divided by twelve months, that is $900 a month, under the line. The year to June 30, 2026 was $13,200, which is $1,100 a month, over it. By the table's own wording, the $900 figure is the one that sets 2026, and the $1,100 figure is the one that would set 2027. Which schedule the shop is actually on is the Department's assignment, not a calculation the tool makes. The tool takes the answer Marguerite gives it.

Scenario one: the 30th schedule, run as the S corporation the shop is. The tool returns twenty-six dated line items. Twelve are sales-tax returns, sixteen of the twenty-six are Indiana's own, and the other ten are federal payroll and federal estimated-tax lines. The Department's table sets the schedule:

> Monthly Filers ... less than $1,000 average monthly tax liability for the prior fiscal year ending on June 30. The January return, Monthly Filers: March 2 (March 1 on Leap Years).

So the December 2025 return is due January 30, 2026, and the January return is due

> 2026-03-02

Two other 30ths fall on a weekend. May 30 is a Saturday and August 30 is a Sunday. The Department's notice states the rule:

> If the due date shown falls on a weekend, federal or state holiday, the payment is due on the next business day.

The April return moves to

> 2026-06-01

and the July return moves to

> 2026-08-31

April 30 also carries the Form 941 for the first quarter, so two filings land on one day. Four more lines are Indiana's individual estimated-tax installments on the owners' returns, on April 15, June 15, September 15 and January 15, 2027, the same four dates as the federal schedule. The December return, due January 30, 2027, is left off, and the tool says why:

> The December 2026 monthly return (due January 30, 2027) isn't listed — this run only checked 2026 dates, which doesn't cover January 2027 yet.

Scenario two: the same shop on the 20th schedule. Suppose the Department moves the shop to the early schedule, which is where $1,100 a month of tax would put it. Still twenty-six items, twelve of them sales-tax returns, each now due the 20th. In most months that is ten days earlier than the 30th. The January return, which was March 2, becomes

> 2026-02-20

Three of the 20ths fall on a weekend, and the returns move to the Monday. June 20 is a Saturday, so the May return is due

> 2026-06-22

September 20 and December 20 are Sundays, so the August and November returns are due

> 2026-09-21

and

> 2026-12-21

The December return, due January 20, 2027, is left off, and the note names it:

> The November 2026 monthly return is listed, but the December 2026 return (due January 20, 2027) isn't — this run only checked 2026 dates, which doesn't cover January 2027 yet.

The shop's tax is unchanged. What changes is that each month's collections leave the account about ten days sooner, twelve times a year.

Scenario three: the frequency not yet confirmed. With everything else answered and the filing frequency left blank, the tool does not guess between the 20th and the 30th. It returns a named refusal: missing: ["how often Indiana has this business file sales tax"]. Nothing on the Indiana sales-tax side computes until there is an answer.

**Scenario four: the identical profile as a calendar-year C corporation, on the 20th schedule.** The tool returns twenty-eight items, not twenty-six. The individual estimated-tax schedule goes, and federal Form 1120 and four Form 1120-W deposits arrive, along with Indiana's own corporate schedule:

> April 20, June 20, September 20, December 20: IT-6 Corporate Adjusted Gross Income Tax Quarterly Payment (Calendar Year Corporation).

The first payment is

> 2026-04-20

and the annual return, Form IT-20, is due

> 2026-05-15

The corporate payments follow the same weekend rule, so they land on June 22, September 21 and December 21. Those are the same days as three of the sales-tax returns for a 20th filer. April 20 carries the first payment and the March sales-tax return as well. On four days a year, two separate Indiana payments fall due together.

What changed

Marguerite has all twelve return dates for 2026 on the same sheet as her estimated-tax and payroll dates, including the two that move for a weekend and the one that lands on March 2. The calendar entry that said "the 30th" is now twelve dated lines. The number to watch is $1,000: the shop's average was $900 for the year that sets 2026 and $1,100 for the year that would set 2027, so the arithmetic points to the 20th schedule for 2027 if the Department applies its own wording. The Department's notice is what settles it.

What the tool will not do

It will not decide which schedule the shop is on. Indiana sets that from a June-to-June average the tool cannot see, so the tool asks and builds dates from the answer. It will not compute the tax owed on any return, and it does not ask whether an Indiana estimated payment is actually owed:

> This tool doesn't ask whether an Indiana estimated payment is actually owed, so it shows the schedule that would apply if one is.

It does not cover Indiana withholding, which matters to a shop with an employee:

> This tool doesn't cover Indiana withholding (Form WH-1, and the annual WH-3 reconciliation due January 31), the Financial Institution Tax, pass-through returns (Forms IT-20S and IT-65), or county income tax.

It will not know about an extension, a payment plan or a penalty already assessed on any date above, and it lists only 2026 dates, so the returns due in January 2027 are left off. 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.