Wisconsin sales tax due dates depend on the filing frequency the Department of Revenue assigns your business. Deadlines fall on either the 20th or the last day of the month following each reporting period, and annual filers get until January 31. Miss the date and you owe a $20 late filing fee plus interest at 1.5% per month on the delinquent balance.
Due Dates by Filing Frequency
Wisconsin uses four schedules, and the deadlines differ by tier. Two of the monthly groups share the “monthly” label but file on different days, which is where most of the confusion starts.
- Early monthly filers (tax over $3,600 per quarter): The return and payment are due by the 20th of the month following the reporting month. January’s tax is due February 20.1Wisconsin State Legislature. Wisconsin Code 77.58 – Returns and Payments
- Monthly filers (tax of $1,201 to $3,600 per quarter): The return and payment are due by the last day of the month following the reporting month. January’s tax is due February 28, or February 29 in a leap year.1Wisconsin State Legislature. Wisconsin Code 77.58 – Returns and Payments
- Quarterly filers (tax of $601 to $1,200 per quarter): Returns and payments are due the last day of the month after each calendar quarter: April 30, July 31, October 31, and January 31.1Wisconsin State Legislature. Wisconsin Code 77.58 – Returns and Payments
- Annual filers (tax of $600 per year or less): The return and payment are due the last day of the month following the close of the calendar or fiscal year. For most businesses, that is January 31.2Wisconsin State Legislature. Wisconsin Administrative Code Tax 11.93
How the Department Decides Your Schedule
The Department of Revenue reviews your sales and use tax remittances over the 12 months ending October 31 and places your account in one of the four tiers above.3Wisconsin Department of Revenue. Annual Filing Frequency Scan It runs that scan every year, so a growing business may be moved to a more frequent schedule and a shrinking one may be moved less frequent.
You don’t get to choose a less frequent schedule than the one you’re assigned. The one exception runs the other direction: if the Department puts you on annual filing and you’d rather file quarterly, you can contact the agency and keep the quarterly schedule.2Wisconsin State Legislature. Wisconsin Administrative Code Tax 11.93 If you’re not sure which tier you’re in, log into My Tax Account or check the notice the Department sent when it assigned your frequency.
Weekends, Holidays, and Mailed Returns
When a due date lands on a Saturday, Sunday, or legal holiday, it rolls to the next business day. If you file by mail, your return counts as timely when it’s postmarked by the due date and reaches the Department within five days after.1Wisconsin State Legislature. Wisconsin Code 77.58 – Returns and Payments Electronic submissions are judged by the date the system receives them, so filing late in the evening on the deadline still works as long as it goes through before midnight.
What a Missed Deadline Costs
Wisconsin stacks several charges on a late return, and they run at the same time.
A flat $20 late filing fee applies to every delinquent return. Unpaid tax accrues interest at 12% per year from the original due date. Once the tax becomes delinquent, that rate jumps to 1.5% per month, or 18% annualized, until the balance is paid.4Wisconsin State Legislature. Wisconsin Code 77.60 – Interest and Penalties
Percentage penalties sit on top of the interest:
- Failure to file: 5% of the tax due for the first month late, plus 5% for each additional month, up to 25% total.4Wisconsin State Legislature. Wisconsin Code 77.60 – Interest and Penalties
- Incorrect return: 25% of the tax due if the Department finds the return contained errors.4Wisconsin State Legislature. Wisconsin Code 77.60 – Interest and Penalties
- Intent to evade: 50% of the tax due if the Department finds you deliberately filed a false return or didn’t file at all to avoid the tax.4Wisconsin State Legislature. Wisconsin Code 77.60 – Interest and Penalties
Each percentage penalty is calculated on the tax itself, not on top of other penalties or interest. Even so, the layers add up fast. A business that files three months late with an incorrect return can be looking at the $20 fee, a 15% failure-to-file penalty, a 25% incorrect-return penalty, and 1.5% monthly interest, all running against the same unpaid balance.
The On-Time Discount You Lose by Being Late
Filing on the deadline isn’t only about avoiding penalties. Wisconsin pays a small retailer’s discount on the sales tax portion of a timely return, and that discount disappears entirely if your payment is even one day late.5Wisconsin Department of Revenue. Retailer’s Discount
- Total sales tax of $0 to $10: the discount equals the entire tax.
- Total sales tax of $10 to $1,333: a flat $10 discount.
- Total sales tax over $1,333: 0.75% of the sales tax, capped at $8,000 per reporting period.5Wisconsin Department of Revenue. Retailer’s Discount
The discount applies only to sales tax, not use tax, and only when the payment is not delinquent. For a business that collects $5,000 in sales tax a month, that’s $37.50 off each return. One missed deadline costs you that discount on top of every other penalty the Department can add.