Recordkeeping for legal protection
Fellow landlords - What sort of recordkeeping system do you use to document that you have performed any routine inspections and maintenance you may be required to perform? I'm thinking of things like smoke/CO alarm testing, rekeying locks, or testing the water heater temperature (120 F max in Wisconsin) where you may someday have to prove that you actually did the work, or simply that you acted in a reasonable manner to provide a safe home for your tenants.
Personally, I just note the date and activity on a spreadsheet, but I'm concerned that may not be considered proof if/when I ever need it. Has anyone come up with a "bulletproof" recordkeeping system that helps provide some legal cover if needed?