Contract assets are recognized in cases where the amount of goods or services transferred to the customer exceeds the amount for which the Group has an unconditional right to payment. Contract assets are regularly reviewed for impairment indicators. Contract liabilities are recognized in cases where the amount of goods or services transferred to the customer is lower than the consideration received or due.

For new installations and modernization contracts, contract balances are recognized on a contract-by-contract basis once the installation begins. The amounts invoiced to the customer are generally based on the achievement of contractually agreed milestones. Such milestones are typically defined as the dates of contract signature, delivery call-off by the customer, and hand­over of the goods or services to the customer. Consequently, the amounts recognized as revenue over time do not necessarily coincide with the amounts invoiced.

For maintenance contracts, contract liabilities are recognized for prepaid maintenance services by customers, whereas contract assets are recognized for work performed ahead of the payment being unconditionally due.