The exact location of the serial number on a guitar varies between manufacturers as well as within models and years of product. Many guitars have etchings of the serial numbers on the headstock or neck plate, while other manufacturers place them on other hardware on the guitar's body. The serial number may also appear on a label within the guitar.
The first place to look for the serial number guitar is on the headstock, which is the uppermost part of the instrument and contains the tuning heads for the strings. For models produced after 1975, the serial numbers for all Fender guitars, excluding vintage reproduction lines, appear on either the front or back of the headstock. Many other brands use this same placement for the serial number, either printing it near the logo or etching it on the back. Fender guitars from 1975 and earlier, as well as other modern and classic guitars from other brands, place the serial number on the metal plate that connects the neck to the body.
Another place to look for the serial number is inside the body of the guitar. The serial numbers on Martin guitars are visible by looking into the sound hole near the location where the neck joins the body, Other brands may place the serial number in the same location, but on a printed label.