http://www.bbc.co.uk/news/uk-politics-44229606
If it goes the way of any other large-scale IT and technology project in the public or private sectors then I'd expect those timescales and costs to double or triple at least.
I'm somewhat sceptical of the claimed £17bn cost for businesses drawing up customs declarations - will British businesses really be employing c half a million more people to add a page of paperwork for each delivery?
All this is based on the "cost" of a customs declaration being £35 - I think the last customs clearance fee we paid to an agent was £12.
The more outrageous claim is that the cost of customs partnership model will be "zero or less". The cost may be zero if the UK keeps the same external tariffs as the EU, but if any tariffs are reduced eg Kenyan beans then I suspect that the cost will be the whole difference in tariffs, based on experience in trying to get a refund from HMRC on customs related stuff.
