My DS has just turned 3 and is fully potty trained on our second attempt. Potty being the operative word.
He does everything he needs to on the potty and we haven't had any accidents since we started but he will not use the toilet. This in itself isn't a problem when he is at home but it means we have to cart the potty around with us on days out etc, as he will go stiff and hysterical if we try to put him on a loo when we are out.
He will sit on the toilet, with the padded seat and a step, at home, my dm's and the cm's if he doesn't actually need to go but he won't entertain the idea if he actually does need a wee etc. He sees us all using the loo and I send him in with his beloved older sister when she's using the toilet so he knows there's nothing to fear!
How do I tackle this? Like I said, it's not a massive issue on a day to day basis but it does restrict us at the weekends or on days out as we are lugging the bloody potty everywhere with us!