Dog trained but urinates in house

Question
Hi, we have a minature short-haired daschund and hes 2 yrs old.  He is trained to go outside to do his business but still urinates in the house daily.  Even if he's outdoors all day while we're at work, when we let him in the house, within 5-10 mins he's pee'd somewhere indoors.  Even if its 2 drops, he marks his spot. Its very frustrating, I dont know what to do!  Please help.

Answer
Hi there
My first question would be is he castrated?  This behaviour is typical of uncastrated male dogs who have issues with thinking they are the alpha male in the house.  If he is not castrated the first step would be to get that done.  However this may not stop the problem completely as the behaviour is already learnt - and obviously if he is already castrated then what you have is a simple dominance issue.
There are a few steps you can take to re-establish yourself as the pack leader within the house.
first enrol in some sort of training class.  A beginners obediance class is perfect and will give you the tools you need to successfully establish a relationship with your dog whereby you are the boss and he knows it!
second you will need to make a few changes to his lifestyle.
1) The dog does not get on furniture - this includes beds sofas, chairs - the lot.  Furniture is for people, its Your domain and he has to respect you enough to stay out of it.  
2) You always eat first.  In a real pack the alpha dogs would eat first and the dogs lower down the pack would get whats left.  When you eat make sure he knows you are eating, do not allow him to beg at the table, send him to his bed while you are eating if he does beg.  when you are finished then he gets his dinner.  
3) never give him anything without him working for it.  This could be a simple sit or a more extensive training routine, but always make sure he does something to deserve his fuss or his dinner, or his biscuit.
Be prepared for his behaviour to take a short downturn as you try to re-establish the correct order in the house, he will see the changes as a threat to his dominance and may act out a bit for a little while, but if you are consistant and firm this should not last very long and he will be happier in the long run for knowing his place.  Being dominant dog is very stressful for him as he always has to worry about challenges to that dominance so he'll be much better off once he knows you are the one who has all that to worry about.
Hope this helps
Sarah