Depends on how old he is. All percs start with 1 bar just after metamorphosis from their larval state (9-14 days old). They fill in their middle bar in the following months and get their tail bar a couple months after that. Some take longer than others, but at about 14 months old, even the late bloomers are pretty much done filling in their white bars. However their orange and black pigmentation still may change as they age, but after 24 months old most of that ceases too.
The description above is for percs. Curiously enough, 1 bar clown species like skunks have 3 bars after meta and lose their stripes as they grow. Perculas add stripes though.
Adult clowns that don't have the same number, shape and size of white bars for their respective species are called mis-bars. Most mis-bars are results of captive bred clowns - thought to be due to "off" nutrition and/or water quality during their developmental stages.
Mis-bar clowns are just as healthy as full barred clowns if coloring is the only thing "wrong" with them. In fact, captive bred clowns tend to acclimate and live better in our artificial environments since they were raised there ... they grew up eating prepared foods, endured wider temp abnormalities and water chemistry swings than their wild cousins.
So ... if you know he is older than 14 months, you almost definitely have a mis-bar. If he's very young he may still grow out his stripes. Either way, if he's healthy and stripes are the only abnormality - enjoy the fish. Nothing to worry about.
