"Does anyone know how late payment has to be before I can start charging interest?"
*** There is no statutory provision spelling out interest due dates. Simply, you can start claiming interest from the date that the debt is overdue.... just make sure that you notify the customer of your interest terms BEFORE they contract with you.
"How much interest can I legally charge?"
*** This is set by the following Kansas statute:
"16-207. Contract rate; penalties for prepayment of certain loans, recording fees; contracting for interest in excess of limitation, penalties, attorney fees; loans excluded.
(a) Subject to the following provision, the parties to any bond, bill, promissory note or other instrument of writing for the payment or forbearance of money may stipulate therein for interest receivable upon the amount of such bond, bill, note or other instrument of writing, at a rate not to exceed 15% per annum unless otherwise specifically authorized by law."
Source:
http://www.kslegislature.org/cgi-bin/statutes/index.cgi/16-207.html
