Companies that exceed their permits must buy extra allowances from those companies who have managed to reduce their emissions - or pay stiff fines. (foeeurope.org)
Will the government just start selling extra allowances if prices get too high? (newrepublic.com)
The key to how much extra allowance you get relies on the proportion (not the amount) of the allowance that your spouse used. (moneysavingexpert.com)