In national and financial accounts, transaction flows record economic activity that occurs during a given period. They capture operations affecting goods, services, labour, capital or financial claims, especially where ownership or control changes or resources are supplied. Flows may be measured directly or inferred from the difference between the stocks recorded at the beginning and end of a period. In the latter case, the calculation must remove changes resulting from reclassification, currency movements, price revaluation or other events unrelated to transactions. The resulting figure is intended to reflect exchanges and other economic operations rather than changes in the recorded value or composition of assets.
Source: European Central Bank (ECB) (source). This glossary entry is an independently worded adaptation of the cited information.