"I had a potential CGT liability but he assisted in having this removed"
Sounds like a bit of "creative acounting". I won't ask!
Acer, I hope my comment wasn't taken as a criticism, your guy obviously works well for you, which is fine. I simply wanted to point out for the OP and others that lawyers/solicitors are not usually fiscal experts, so a gestor would normally be who you would turn to for tax matters. For "conveyancing", if the term even applies in Spain, when buying it is advisable to use a lawyer; when selling, there's very little if anything for them to do - nothing in fact that an estate couldn't do for their sale fee, if one is involved.
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I must admit I have never heard of an estate agent charging seperate fees to both buyer and seller - at least, not officially. I have come across agents adding on more commission to the sale price without the seller's knowledge or consent, which I suppose amounts to the same thing in a way. Either way, I would question the statement "I have never paid an agent for purchasing a property". Unlike in the UK, where an estate agent usually "values" the property and suggests an appropriate market price, in Spain it is more normal for an agent to simply ask the seller how much they want for the property, and then add their 3 or 5 or 7.5% on top, meaning the buyer in reality is paying the commission. This is certainly what happened last time I put a property up for sale: I put a Se Vende sign in the window, and when I established that a caller was an agent, I told them the price I had quoted was the price I expected for me, any commission they wanted had to go on top of that. Hence, if they brought a buyer, it would in reality be the buyer paying the commission - albeit probably without them realising it. Unless, of course, having seen my number in the window they subsequently called me directly pretending to be a new caller, and got quoted a lower price. It has happened more than once! I wouldn't do it myself, and I agree it is unethical, but if a potential buyer wants to try cutting out an agent who I never approached in the first place & never signed any agreement with, I don't really have a problem with that. (Different story if I had in fact listed the property with that agent). But I would make it quite clear to that buyer that I will accept no responsibility if the agent finds out and gets shirty!