£ MillionsDevelopment costsBrandTrademarksTechnologyCustomer
Customer contractsIntangible softwareIntangible software
under development
At 1 January 201725.
Acquisition of business4.90.35.2
Foreign currency translation(1.2)(0.1)(1.3)
At 31 December 201729.
Reclassification from property, plant and equipment0.50.5
Acquisition of business0.82.612.10.215.7
Foreign currency translation1.
At 31 December 201836.
At 1 January 201710.
Charge for the year2.
Foreign currency translation(0.3)(0.1)(0.1)(0.5)
At 31 December 201713.
Charge for the year2.*5.7
Foreign currency translation0.
At 31 December 201816.*21.1
Carrying amount
At 31 December 201820.
At 31 December 201716.

*Balances are less than £100,000.

The amortisation period for development costs incurred on the Group's products varies between three and seven years according to the expected useful life of the products being developed.

Amortisation commences when the product is ready and available for use.

The remaining amortisation period for customer relationships ranges from three to nine years.