For state specific - there are no statutory limits on commercial loans that I know of.
Here is the info on consumer loans:Late payment charges are governed by Section 138.05(3), Wis. Stats. (PDF: external link), on purchases for individual, family or household purposes. Finance charges on consumer transactions are regulated by the Wisconsin Consumer Act.
As far as regulation Z if it is a commercial loan it is exempt from that rule:
Sec. 226.3 Exempt transactions.
The Federal Reserve Board's Regulation Z (12 CFR Part 226) has been republished effective December 30, 2011, at 12 CFR Part 1026 as one of the regulations transferred to the Consumer Financial Protection Bureau under the Dodd-Frank Act. This section of the FRB regulation was republished as §1026.3 of the Bureau's regulation.
This regulation does not apply to the following:
(a) Business, commercial, agricultural, or organizational credit.
(1) An extension of credit primarily for a business, commercial or agricultural purpose.
(2) An extension of credit to other than a natural person, including credit to government agencies or instrumentalities.
Hope that helps!
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