Since I am not blessed with a bottomless wallet I try to get as much out of my flying-budget as possible. One way to stretch my funds has been to take advantage of the European Directive 2003/96/EC which says that fuel NOT used for private pleasure flying should be tax-free or the tax refunded.
iAOPA has an overview as to where you can get a refund. Here is my real life experience.
Sweden:
Refund: 0,68€ pr litre How: Upon homecoming I fill in this form and send it according to the instructions together with the receips. 1 – 2 months later the refund is on my account, no questions asked. Minimum amount in order to get refund is 100 litres.
Important: Your flight must not be a commercial operations. It is enought that the purpose of it is related to work/business.
I’ve heard that Denmark is equally cooperative but have never tried.
Norway
Refund ca 0,65€ pr litre. If your destination is abroad you can get a tax refund (actually, the tax is never charged). How: Pay with credit card and e-mail or fax a copy of the logbook page to the fuel company before the money is drawn from the card.
Poland
Refund: Ca. 0,6€ pr litre The fuel companies operate with a list of approved commercial operations. In order not have to pay the tax, you should be on that list. However, some times I’ve been lucky (by bringing a company statement with me) and ended up with a fuel price of 1,6€. If you fly out of Poland they will not charge you for VAT if a business is paying for the fuel (the fligh must not be commercial).
If you opearate in theese areas, wIth a little fuel planning there are hundreds of € to be saved. I've calculated that I need 22 flight hours to save 1000€.
If others add countries/places we could end up with a list of smart fuelstops.
That is really interesting information.
I know that a lot of people in the UK have been asking if any other country has the equivalent of UK's duty drawback.
There have been rumours that Italy does something similar, but nobody was able to find out any more.
That explanation (in the AOPA link) about why Italian clubs won't sell avgas to foreigners is one I have heard a number of times. However (I am told) if you can make a discreet approach to somebody in the club, they will sell it to you, by pretending they are filling up one of their own planes. Fairly obviously this requires that you speak Italian 
Up to some years ago, one could obtain tax free fuel by saying the word "commercial" to the pump man, 3 times, loudly It used to work especially in Spain, though in some places it would help to wear the full pilot uniform. I used to do this, and others I knew at the time used to do it too. Having an AIR BP card with a Limited Company name on it was also helpful. But that's all been stopped.
You can still get tax free fuel everywhere (except the UK) if you have an AOC, and it doesn't matter whether the AOC is relevant to the flight. I always ask, and I always get the same answer. Even in Greece... For this reason, a commercial operation (say a school) may find it worthwhile to obtain an AOC for "something, anything" and then they can get tax free fuel everywhere they go. The saving is huge, obviously. I think you can get the most basic AOC done for about €10k. I know somebody who (more than 10 years ago) got an AOC for traffic spotting for a local radio station. He did it because the man funding the business was stupid, which was good for employment
In the UK, AFAIK, an AOC holder has to apply separately for the refund - like one applies for the duty drawback.
It's very interesting that one can legally apply for the refunds, though I suspect that most countries will place so many obstacles in the way that it won't be worth doing.
OK, here are my suggestions for "cheaper" Avgas (in relative terms...) for those who neither have an AOC, nor fly for business:
Germany: fly to and refuel at Helgoland EDXH. This island in the North Sea (most British people interested in history will know it...) has some kind of special customs status; therefore you can buy Avgas at around 1,90 Euros (doesn't matter where you are headed to). I buy most of my fuel there. But beware: the longest runway is only 480 meters long (asphalt and no significant obstacles) and the wind can be strong and gusty. Unfortunately, it does only allow German language on the radio.
Italy: when refuelling and departing towards a non-EU country (Switzerland for example), you can, in principle, get duty free and tax free fuel. Unfortunately, I don't have any personal experience from when I lived there. The most recent "pirep" I received is from 2011, when a pilot flying to Croatia paid about 1,40 per litre at Pescara airport.
Luxemburg: if leaving towards a non-EU destination, you can get very cheap Avgas. Someone reported 1,66 Euros this january.
Channel Islands, obviously (more or less 1,85 Euros currently).
UK: duty free fuel for all flights abroad. You save about 45 Euro cents over the regular price. With the lowest "regular" prices being about 2,25 Euros (about 1,90£) currently, it can effectively get as low as 1,80 Euros. Strangely, it seems like a few airfelds (but not many) also deduct VAT for flights abroad (Gloucestershire and Dunkeswell, reportedly), allowing even lower prices. I have personally experienced this at Enniskillen only (great!).
Ireland: again, no personal experience, but prices can reportedly go slightly below 2 Euros if flying abroad. Unfortunately, I have heard that this now going away due to some change in irish legislation.
Poland: as already reported, it is possible to find Avgas at prices slightly below 2 Euros, even without any duty or VAT reductions. This site can give you an idea about price relations between different airports (it is difficult to actually calculate total prices in Euros because certain taxes apply on top of the reported prices).
UK: duty free fuel for all flights abroad
Need to be a bit careful about that.
You can claim only for fuel exported which is not the subject of a previous claim.
I know it's obvious but if others have been flying the plane it can sometimes be hard to tell.
Interesting that some regard below €2 as cheap! I would say €1 is cheap, and probably almost possible if you could get all the duty and VAT removed.
A lot of UK pilots fly to the Channel Islands for the cheaper fuel, usually but not always on the way to France. Unfortunately, to get the full advantage, they tend to leave the UK with minimum fuel, and don't always make it all the way there 
In reality the benefit of leaving the UK with full tanks, claiming the duty drawback, and avoiding the C.I. (approach and climb, and extra distance flown) is probably as good.
Let' face it. Full blown average prices (in Euros) for 100LL nowadays are:
Germany 2.70, Austria 2.40, Switzerland 2.45, France 2.30, Spain 2.80, Italy 2,90, Greece 3.00, Netherlands 3.00, Belgium 2.60, UK 2.50, Ireland 3.00, Denmark 2,60, Czech 2.50, Croatia 2.30, Slovenia 2.30, etc.
So yes, definitely...for "private flyers" anything below 2 Euros is a real good deal nowadays. Sad but true.
I would say €1 is cheap, and probably almost possible if you could get all the duty and VAT removed.
Current US prices are just slightly above that including tax, so yes.
Its frustrating just reading about fussing about with VAT, never mind doing it.
Italy: when refuelling and departing towards a non-EU country (Switzerland for example), you can, in principle, get duty free and tax free fuel.
I confirm.
Can you describe the procedure for getting it, AfricanEagle?
Lots of people have asked over the years but nobody ever came up with the details of the Italian procedure.
You declare you are going to a non-EU country, fill up and pay duty free fuel price. Arriving at destination you are required to fax back to the refueller copy of arrival form or landing fees receipt within a few days, otherwise they’ll send you the bill for full price.
But surely that will only work when buying under the “standard” condition, which seems to be rare because where AvGas is available, it is mostly under the “club” regulations?
