[2009] EWCA Civ 170, 10 March 2009. The case relates to the reopening of invoices already paid and recovery of payment. Elecref Limited (E) was a subcontractor supplying electrical items. Furmans Electrical Contractors (F) installed the cabling for E. The payment was according to the amount installed. From about July 2004, E decided to pay the works according to daily rates, which were increased to include accommodation when the site was far away. E paid F's invoices until September 2007. Then it notified that the invoices were too expensive because F's men were working fewer hours and because they were paying for accommodation on Fridays which were not used on that day. E did not ask for recovery of overcharged amounts but paid a further sum of money to F. E refused to pay further invoices afterwards. F issued proceedings to the court. The judge concluded that F had to repay E the sums overcharged. The case was appealed. "Held": Appeal dismissed, the respondent's appeal is allowed. The judge erred in failing to distinguish between the paid and unpaid invoices. There was no basis to reopen the invoices already paid to F. F's invoices claiming the daily rates were not contrary to any agreement or representation. In not claiming the recovery of the money and making a substantial payment afterwards, E waived any claim to recover this money. F was entitled to judgement in the appropriate sum.