Wisconsin Sales & Use Tax Return — Form ST-12

Determine whether the business has Wisconsin sales tax nexus (physical presence and/or economic nexus at $100,000 in gross sales into Wisconsin — revenue only, no transaction-count test). Confirm whether a Seller's Permit is already active or needs to be obtained via My Tax Account. Identify the correct filing frequency (monthly/quarterly/annual) based on prior-year liability.

Classify all products and services sold into Wisconsin by taxability under Wis. Stat. Chapter 77. Apply destination-based sourcing (SST rules) to assign the correct combined rate: 5% state plus the applicable county option tax (0.5% if the customer's county levies it, up to 5.5% maximum). Flag any edge cases — SaaS (not taxable), grocery food (exempt), clothing (taxable), enumerated services (landscaping, telecommunications, lodging, parking, admissions).

Audit exemption certificates received from customers claiming resale, manufacturing, agricultural, government, or nonprofit exemptions. Verify each Form S-211 or S-211E (or SST Streamlined Certificate) is complete, current, and properly retained. Identify any certificates that are missing, expired, or incomplete — those sales must be treated as taxable on the ST-12.

Identify any taxable items purchased by the business for use, storage, or consumption in Wisconsin on which Wisconsin sales tax was not collected by the vendor. Common examples include out-of-state purchases, online purchases from non-collecting vendors, and items withdrawn from resale inventory for business use. Calculate use tax at 5% state plus applicable county rate.

Compile gross sales, taxable sales by county, exempt sales, and use tax into Form ST-12 (Wisconsin Sales and Use Tax Return). Calculate the 0.5% retailer's discount (maximum $1,000 per period) available for timely filing and payment under Wis. Stat. Section 77.61(4)(a). Verify the return period matches the assigned filing frequency and confirm the due date (monthly: last day of following month; quarterly: last day of month after quarter-end; annual: January 31).

Submit the completed ST-12 electronically through My Tax Account (tap.revenue.wi.gov) — electronic filing is required. Submit the associated payment on or before the due date to preserve the retailer's discount and avoid penalties (late filing: $20 or 5% per month up to 25%; late payment: 1% per month; interest: 12% per year). Confirm receipt and retain the confirmation number.