Madison Teachers, Inc. (PDF), via a kind Jeanie Kamholtz email (PDF):

The Department of Public Instruction receives 36,000 teacher license applications each year (initial and renewal applications). To help make this process more efficient, DPI created the Educator Licensing Online (ELO) System in December, 2013. DPI no longer accepts paper applications for license renewal; one must complete and submit the renewal application through this online system.
Don’t wait until the last minute to prepare for a license renewal. If your license is set to expire on June 30 of this year, start collecting the required documentation early. You will need to provide information about the certifications currently held (they can all be renewed), and where and when you completed your certification (you can provide multiple IHEs). If you were licensed in 2004 or after, you must have your PDP reviewed and approved. Once that is accomplished, the District will provide that information directly to DPI.
If you are renewing your license through the completion of 6 university credits, have electronic (scanned) verification available, so it can be uploaded during the application process. All applicants will need to complete a Conduct and Competency Questionnaire and will need to scan and upload an Employment Verification form (#1613) signed by MMSD Human Resources. Using the new system the first time can be confusing and frustrating. Having all the information and/or materials you need, will help to make the application process go more smoothly.
A one-time, one-year license extension is possible. Failure to renew one’s license can be considered a severance of one’s teaching contract, and will be considered a resignation by the District.
Contact MTI for assistance or questions about your license renewal. For more information visit DPI’s ELO website: http://tepdl.dpi.wi.gov/licensing/elo.