well, since it used to be my job, i can explain how it works in the uk if you want, as it should the same in every EC country (with slight differences from country to country for their operating procedures), since we are all just one super state according to brussels....
although french beer duty is actually a lot less than ours. they pay roughly 4 pence tax per pint, we pay about 27p, if not more. each country is entitled to make up their own excise duty rates, but procedures should be roughly the same so we are all playing by the same set of rules. but then this is france we are taking about here......
normally a brewery will pay duty on the beer once its brewed based on the alcohol content, unless they hold it in an Excise warehouse and then its suspended till its removed for onward sale/bottling etc, but thats another story, and i assume JY just pays his duty upfront if he's liable.
beer duty in the UK is £13.26 per 1% of alcohol per hectolitre of beer, so if your beer is 5%ABV, then you multiply £13.26 by 5 to get £66.30 plus vat at 17.5%, per hectolitre of beer.
typically, if you brew something and it goes off, it is possible to reclaim the duty, but you do need to jump through a few hoops to get it. C&E are a nasty bunch of people to get money out of when it comes to excise duties.
however, small producers of beer are entitled to a discount on this duty of 50% as long as their output is less than 60,000 hectolitres per year, again, i think this limit is different in france though.
http://customs.hmrc.gov.uk/channelsPort ... _CL_000232 the C&E beer duty information booklet if you fancy a boring read. its not for the faint hearted though.
 :stun 
i've put 2x 3 kw heat element.
but on the morning the liquor was still at 65° 
