As shown in the image above the service tag is as mixture of characters and numbers whilst the serial code or service code is just a sting of numbers. The dell service tag is different from the serial number but they both perform the same function.
Also note if your computer shows the express service code that will work to as it can be converted to a service tag and the other way round Dell Optilex computer with service tag sticker Is the service tag same as serial number? It is usually located at the bottom of laptops and back of desktop computers next to the windows product key on most computers. The dell service tag is a 7 digit character code usual a combination of letters and digits that is specific to your device. When ever your computer has problems, you need to have the service tag as customer service will request for it.