We trained at 18 months. He wasn’t showing any “signs”. We just had a decent break over the Easter holidays and felt it was a good time to try. Honestly, we fully expected it to not go well and were completely happy to stop and try again at a later date. However he did really well!
Yes, it took a bit longer to get him fully reliable than it might have taken with an older child (but not necessarily, I know people who struggled more with their 3 years olds. There’s more to it than age). However he was doing so well that his nursery agreed that we should keep going.
He did need a bit more help to manipulate his clothing and get on and off the toilet as he was smaller. His language skills were limited so it wasn’t as easy for him to tell us that he needed the toilet, but we used a sign for a while. I’d prompt him every 2 hours if he hadn’t been. So he wasn’t potty trained at that age as in he could go completely independently to the toilet alone, wipe his own bottom and wash his hands.
However he was totally out of nappies during the day and could hold his bladder for 2 hours, so he must have been ready on some level.
We absolutely wouldn’t have forced the issue if he wasn’t able to hold his bladder for a reasonable length of time or was getting upset. But I think it was right for him.
With my second child, I might leave it a few months later, just until that language burst which would have made things a little easier. But I fully intend to try around 20-24 months. And it might not be right for him and he might need to wait until later. It’s different for all children.
However I just wanted to share our experience as I always see responses to this question as “you need to see the signs” and “18 months is too young” and it’s simply not true for all children. You can try, with a no pressure approach and accept that it may not work out. But it also might.