We got a phone call today from a couple that bought a puppy off of us in the summer so the puppy is 5 months old this weekend, anyway they seem to be having problems with getting the puppy dry as he still has accidents inside. All of our dogs have been clean from about 12 weeks of age excluding the odd accident but otherwise are good.

They say they take him out regally throughout the day but he refuses to pee outside waiting till he gets to the garden, but he will also mess inside even if the door is open. We are going to visit in a week or so to see the problem first hand to see if he is anxious or whether the owners need a helping hand in the right direction regarding toilet training. (They have had dogs before).

Its not really a problem Iv come across before has anybody got some tips.

Cheerz

Did they use any training aids to start with? Like puppy pads or newspaper and start the training that way? That seriously can hinder the time it takes, which you will know.

I wonder how long they are in the garden with him for and if they get him moving about to try and get it moving so to speak?

Yep agree with that Sue, I used puppy pads and newspaper at night in the beginning for Vic and he took so long to come clean. Someone advised me to get rid of the newspaper/pads completely and he improved no end, he was still having occasional mistakes till he was 9 months! old though, probably because of the puppy pads.
Around that time he came away with me for a week to my dads house and was clean the whole week and has been everywhere else since so I think the change of location helped break the habit for him.

It took until our dog was about 7 months old until he would wee & poo on walks, he's always preferred the garden. Even now if we're at friends houses he'll hold it, so we never visit for long!!! I was always told to give him time and it will eventually happen and it did. I'd agree with no puppy pads, we never used them but unless there's something wrong, my advice would be, be patient.

suejaw has a very good point.  How long do they stay with him?  You say that he does it inside (even if the doors are open.)  Them being open is irrelevant.  They should have been staying with him from day one.

What do they call "taking him out regularly?"

Tell them to get back to basics, as if he was an 8 week old pup.  Outside, every hour, on the hour.  And stay with him.