The tobacco company agreed the €1.2bn (£1.1bn) sale in two parts of its handrolled cigar business in April to cut debt.
Purchasers Gemstone Investment and Allied Cigar Corporation made a non-refundable down payment of €91.7mln and agreed to pay another non-refundable payment of €85mln to Imperial by October 7.
Imperial also agreed to provide a six-month vendor loan at completion of up to €250mln while the purchasers finalise long-term financing arrangements.
The Premium Cigar unit, which is made up of US-based Tabacalera and four 50%-owned joint ventures with the government of Cuba to export hand-rolled Cuban cigars, contributed £226mln of net revenue and £80mln of profit before tax in the last full year.
Shares rose 1% to 1,404.9p on Monday in early trading.