Lakeshore Outfitters files one Michigan return for sales tax and withholding, and a C corporation would owe eight state and federal estimates in seven different months

The moment

Lakeshore Outfitters is an outdoor-gear retailer in Holland, Michigan. Renata Voss and her brother Ilya took it over from a retiring owner in 2021. The shop sells kayaks, paddles, tents and camping stoves, rents boats in summer, and has one W-2 employee besides the two of them. It is taxed as an S corporation. Michigan sales tax is collected at the counter, and the employee's Michigan withholding comes out of every paycheck. It is the last day of September, and Renata is building next year's tax sheet, as she does every fall.

What they did instead

Renata kept two reminders on her phone: "sales tax, the 20th" and "payroll tax, ask Dee." Dee is the bookkeeper. Every quarter Renata asked her whether the withholding had its own date or rode with something else, and every quarter Dee said to check the return. Nobody had put the answer on the sheet. She also never saw that June 20 and September 20 are weekend days this year, so the reminder went off two days before it needed to. The cost was not a penalty. It was about four short questions a year to a paid bookkeeper, and a habit of filing on the wrong day of the week because the reminder said the 20th.

The questions a CFO asks first

1. How many Michigan return dates does the shop have in 2026, and which of them move for a weekend?
2. Does the employee's withholding have a date of its own, or does it ride with the sales tax?
3. What would the year look like if the Department assigned the shop quarterly or annual filing instead?
4. What does a Michigan calendar-year C corporation owe that an S corporation does not?

The arithmetic, shown

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

Scenario one: monthly, the schedule Lakeshore is on. The tool returns twenty-six dated line items. Twelve are Michigan's monthly returns, four are Michigan estimated-tax installments on the owners' returns, and ten are federal payroll and federal estimated-tax lines. The Department's form instructions state the date:

> Form 5080: This return is due on the 20th of the month following the return period.

The form covers more than sales tax:

> Sales, Use and Withholding taxes are filed on a monthly, quarterly or annual basis. A filing frequency will be assigned upon a taxpayer's estimated level of activity.

So the withholding does not have a date of its own. One return, one date, three taxes. Twelve months, twelve returns: the January return is due January 20, 2026, and the April return is due April 20. Three 20ths fall on a weekend in 2026. June 20 is a Saturday, September 20 is a Sunday and December 20 is a Sunday. The Department's rule for this:

> If the due date of your return falls on a Saturday, Sunday, or one of these holidays, your payments must post on the next business day immediately following the weekend or holiday.

The June return moves to

> 2026-06-22

the September return to

> 2026-09-21

and the December return to

> 2026-12-21

All three are Mondays. The Department adds a rule for paying electronically:

> If you pay by Electronic Funds Transfer (EFT) method your transmission must be made on business day before the due date.

Read plainly, a payment due Monday June 22 goes out the Friday before, June 19. The tool shows the return date and does not compute the transfer day. The individual estimated-tax installments fall on April 15, June 15, September 15 and January 15, 2027, the same four dates as the federal schedule, so on each of those days the owners have two payments. The December 2026 return, due January 20, 2027, is left off, and the tool says why:

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

Scenario two: quarterly, or annual. Suppose the Department assigns a lower-volume schedule. On the quarterly schedule the tool returns seventeen items, and the sales-tax returns fall on

> 2026-04-20

> 2026-07-20

and

> 2026-10-20

Three returns replace twelve, so the shop has nine fewer Michigan dates. The fourth quarterly return, due January 20, 2027, is left off:

> The Q4 2026 quarterly return (due January 20, 2027) isn't listed — this run only checked 2026 dates, which doesn't cover January 2027 yet.

On the annual schedule the tool returns fifteen items and exactly one Michigan sales-tax date. The form instructions say:

> Form 5081: File this return by February 28, 2027.

February 28, 2027 is a Sunday, so the Department's weekend rule moves it to

> 2027-03-01

A Monday. An annual filer has one Michigan return for the year and it falls in the calendar year after the one it reports.

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 Michigan has this business file sales tax"]. Nothing on the Michigan sales-tax side 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-six. The individual estimated-tax schedule goes, and federal Form 1120 and four Form 1120-W deposits arrive, along with Michigan's own corporate income tax schedule:

> Calendar Year Filers: First Quarter – April 15. Second Quarter – July 15. Third Quarter – October 15. Fourth Quarter – January 15, the following calendar year. Annual – April 30, the following calendar year.

The federal deposits are April 15, June 15, September 15 and December 15. Michigan's are April 15, July 15, October 15 and January 15. Only April 15 is shared. Eight estimated-tax dates, in seven different months, where the S corporation has four dates in four. Michigan's annual return is due

> 2026-04-30

and Form 941 for the first quarter is due the same Thursday, so two filings land on one day. Michigan's second and third payments are

> 2026-07-15

and

> 2026-10-15

a Wednesday and a Thursday, each a month after the federal deposits that precede them. A cash reserve built to the federal dates would be drawn down again a month later.

What changed

Renata now has all twelve return dates for 2026 on the same sheet as her estimated-tax and payroll dates. The reminder that said "the 20th" is twelve dated lines, three of which are Mondays after a weekend. The question she asked Dee every quarter has an answer on the page: the withholding rides the same return as the sales tax. The number to watch is the filing frequency. Twelve dates, three dates or one date is the Department's assignment, and it changes the size of this sheet by more than any other single answer.

What the tool will not do

It will not decide which schedule the shop is on. Michigan assigns the frequency from the business's estimated activity, so the tool asks and builds dates from the answer. It will not compute the tax owed on any return. It covers the base dates and leaves out what the Department also has:

> This tool doesn't cover Michigan's elective Flow-Through Entity Tax, city income taxes (Detroit, Flint and others), the "Accelerated" filer tier that Form 5080's instructions name, or Michigan withholding for a business that collects no sales tax

Two of those matter here. A shop the Department moves to an accelerated tier would have dates this sheet does not show, and a shop that elects the Flow-Through Entity Tax would owe a payment the tool does not know about. The tool also does not ask whether a corporate payment is owed at all:

> a Michigan corporation with less than $350,000 in allocated or apportioned gross receipts, or $100 or less in annual liability, isn't required to file or pay the corporate income tax. This tool doesn't ask

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.