Let's talk about how to deal with toilet training regression. When children are fully potty trained, they should be using a toilet on their own and having very infrequent accidents. Sometimes kids will regress and start having more frequent accidents or refusing to go to the potty. This can happen if there's a new baby in the family, if there's a move or another significant live change so what you need to do in order to deal with a regression is first to give the child a motivation to use the potty. This is where the rewards come in. Every time your child has a success in the potty and keeps his pants dry, he needs to get a reward. This will encourage him to use the potty frequently and this will discourage his accidents.
Also if you build in a natural consequence for when he does have accidents, that will discourage him from having them in the future as well. Often times kids will start to regress when a new baby arrives because they want to be like the baby so you want to make sure that they don't have the option to use a diaper at all anymore. You want to tell them that the diaper is only for the baby and they're a big kid now and they need to wear their big kid pants. And that's how you deal with regression.