Not necessarily, some are printed inside.

If the sweater you bought does not have a trademark, take it to the store to return it for a refund. If you buy it in a physical store, there are two reasons. 1. This piece of clothing has been worn by others, so it has no trademark; 2. This sweater is not an authentic sweater produced by a regular manufacturer and has no trademark at all!

If you really like this sweater, you don’t have to worry about whether it has a trademark or not. As long as the sweater is in good condition, it doesn’t matter whether it has a trademark or not.