sales people don't usually have adequate training and education in the area to be able to 'diagnose'.  As a child, I had bad feet.  My parents took me to a dr who diagnosed me as having recurrent plantar warts, that were regularly removed.  They were not actually warts, but build up of toughened skin as the result of sharp bones rubbing against the bottom of my feet.  once we had changed drs, a few years later, the real problem was identified and I was sent to a podiatrist. by wearing orthotics (not store bought but specifically made for me) in my shoes, my feet improved a little but it was caught too late and my feet were unable to be fully corrected.  Had my first dr correctly diagnosed the problem in the first place, I may not have the problems I have now.  as an adult i now suffer from a bad hip, knee pain and leg aches due to my feet problems.  long story short- see a podiatrist to be sure and yes, it can cause problems down the line.

I would confirm it with a doctor, know what your options are, is it necessary to buy custom made shoes or is it perfectly fine to wear normal shoes. If this is something he needs expensive shoes for, then proceed to buy. If not, take him to spend less hahaha unless he is lucky enough to get brand name shoes anyway.

I was interested myself in Flat Foot and what it might mean for a child and found the following link.

http://www.chw.edu.au/parents/factsheets/flatfetj.htm

My gut reaction when a childcarer suggested my son might have flat foot was "so what" not because I didn't care but because something in the back of my head said if it's not causing pain it can't be a big issue.

I had intense foot pain at one point in time... and the doctor told me I had flat feet. The pain when straight down though my arch and then shot towards my heel. The solution was to get shoes with lots of arch support. Which are very expensive. I was in univeristy, and couldn't afford that. So, I found a pair of shoes with almost no arch in them, cut up some plastic shopping bag, and shoved that in my arch. It actually worked better than the commercial inserts I got later. Why did this work better? Because my feet are two different sizes (almost 11 and just over 10) and so the archs in most shoes aren't in the right places for me.

So, with all this, i figured out a couple things.( I could very well be wrong here, so Minti people may have more accurate info and need to correct me again, as these are just my own thoughts on the matter.) To me, feet have two positions. Up right, like when your wearing high heels and there is lots of support on the sides holding your foot slender. And kindof flat, like when you've been going barefoot for weeks. They told me not to go barefoot any more, that that was the problem. Umm... I've found that if i have too much support alnd don't go barefoot enough, that is when I have problems. So, maybe I'm making a real problem worse (although I have no pain or other identified problems...), or maybe they just think feet are supposed to be upright, and in shoes! (i was a barefoot kid, and I'm a barefoot adult... even in church, but that's different!) I was one of those babies that your always making sure you have their socks before you leave!

I would take him to get them looked at properly. yes they might know what flat foot is and stuff but to go to the person that can tell you for sure what it is like and to give you the best insole and shoes for his feet would be better!