Determine what brand of lawn mower you own. Different lawn mower manufacturers put the serial identification number in different locations. Your lawn mower's brand name should be displayed prominently on the machine itself.
Determine where your lawn mower manufacturer typically puts the serial numbers in one of a handful of places. Husqvarna, Sears and EHP put the serial numbers on the back of the lawn mower housing. Toro, MTD and John Deere put the serial number on the underside of the seat of riding mowers and on the decks of push mowers. If you do not find the serial number in these locations, check under the handle on your push mower, on the underside of the frame, above the wheels or on the box.
Examine the lawn mower closely and look for the serial number. Most manufacturers use a decal or plaque that has the serial number printed or stamped on it. The plaque or decal should be between 2 and 3 inches long in most cases and will list the model and serial number of the unit. The serial number is your identification number.