It's a prudent business practice to keep track of products not only for quality control but also for verification of ownership and registration. Serial numbers were created by the International Organization for Standardization (ISO) in 1975, and they are assigned by using the International Standard Serial Number (ISSN) protocols--a universally recognized numerical coding system.
Toshiba is a major electronics manufacturer that uses serial numbers to account for products the company puts on the market. The serial number is important to Toshiba and to you, as the consumer, so Toshiba makes it easy for you to locate that serial number on your laptop.
Prepare your laptop for inspection. To be on the safe side, power down your laptop and close the lid. If you have any peripherals or cords connected to your laptop, temporarily detach those items so they don’t impede your ability to maneuver the laptop. Gently turn your laptop upside down, preferably on a table or other hard surface. To avoid scratching your laptop lid, place a cloth or towel under it.
Examine the laptop for the serial number. As laptop models change over time, so will the exact position of the label, but Toshiba tries to keep the serial number label on the underside of the unit. The label itself is usually a black and gray sticker. The actual serial number will always be labeled with the words “Serial No.”
Record your serial number. Don't forget to include letters that are part of the complete serial number.
Upright your laptop. Turn the unit right side up. You can then reattach any peripherals and cords.