Since $1981,$ each on$-$road vehicle sold in the US has been required to have a $17-$character VIN structured and constrained as follows:

A three$-$character $($alpha$-$numeric$)$ world manufacturer identifier $($WMI$).$ Excludes I, $O$&$Q$

A five$-$character $($alpha$-$numeric$)$ vehicle descriptor $($VD$).$ Excludes I, O & Q

A single $($numeric or $\text{'}x\text{'})$ check digit $($CD$).$ The digit is calculated from the other $16$ letters$/$digits $($and is used for detection of invalid VIN$).$

A one$-$character $($alpha$-$numeric$)$ model year $($MY$).$ Excludes $\text{'}$I$\text{'},\text{'}$O$\text{'},\text{'}$Q$\text{'},\text{'}$U$\text{'},\text{'}$Z$\text{'},$ & $\text{'}0\text{'}($zero$)$

A one$-$character $($alpha$-$numeric$)$ plant code $($PC$).$ Excludes I, O & Q

A six$-$character $($alpha$-$numeric$)$ serial number $($SN$).$ Excludes I, O & Q

Note that any letters used will only be UPPERCASE, and the letters I, O$,$ or $Q$ are never use for any part of the VIN.