The timing of recognition for share-based payment transactions related to services is determined based on the period over which the associated goods or services are received. According to the terms provided, the correct statement about timing is:

Services are recognized as they are received.

This aligns with the principle outlined in the accounting standards, such as IFRS 2, which dictates that the cost or expense related to share-based payments for services, like employee stock options, should be recognized over the vesting period, which is typically the period during which the employee provides their services to the company. In this case, as services are rendered over time, the related expense is recognized proportionally over the service period.