A boy should be able to wipe himself by age 2 to 4 years although or when they are potty trained.
However some boys may still need help wiping their bottoms until after 4 years old and sometimes until 5.
Some boys need a bit longer to master the skill of wiping themselves after pooping in the toilet depending on their dexterity and individual development.
Being able to wipe yourself is one of the last steps in potty training and is best taught as soon as they begin to use the toilet independently.
It's okay if the child needs some help wiping themselves for a bit longer than normal.
My son was potty trained by 3 years old but he needed help to wipe himself until he was 5 as he would sometimes even forget to wipe.
I would often find poop stains on his underwear so I would have to check him to make sure he wiped.
Sometimes he wiped and sometimes he didn't.
Eventually your child will start to wipe themselves without any help.
By the age of 5, most children should be capable of wiping themselves effectively.