Mossberg serial number location?

[Ukraine Train]

I have a Mossy 500 20" and for the life of me can't find the serial number. Under the heat shield maybe? There's a number written on my bill of sale so I know it's on there somewhere.

 

[Kevlarman]

It's on the left side of the receiver, right above the trigger group. If you've installed a sidesaddle on the gun, it's underneath that and you won't be able to see it.

 

[Ukraine Train]

If you've installed a sidesaddle on the gun, it's underneath that and you won't be able to see it.

Oh, that explains it lol. Thanks.