I used a positive parenting approach with both my children when younger - no time outs, no punishments, consequences and boundaries, avoiding shouting and no smacking - and it worked really well, especially with my DS1 who is head strong, strong-willed, prone to dramatics and impulsive. He is definitely an experiential learner - "because I say so" has never worked with him, he needs to work out or experience for himself why he should / shouldn't do things.
He's 11 now, and clearly we need to change our approach somewhat - or maybe we don't?! He plays Fortnite with friends online, and managed to spend 50 euros on v-bucks before we noticed what was happening. When asked about it, he admitted he knew what he was doing, he just wanted them so much that he didn't think about the consequences. He often says he is scared to tell us when he has done something wrong as he's afraid of getting shouted at.
What is the positive parenting way to approach this with an argumentative and hard-done-by tween? DH feels strongly that he needs a should be punished for this, otherwise he won't learn anything and he'll 'just get away with it yet again".