An effective accounting system should identify and record only the valid transaction of the entity that occurred in the current period, which relates to the

Existence or occurrence assertion

Explanation:

In simple words, The existence as well as occurrence allegation determines whether assets and liabilities occur at a specific date and if activities have been documented. If fraudulent sales were reported, there would be a deception. Exaggeration of financial stating parts is a major risk here.

Thus, from the above we can conclude that the correct answer is existence or occurrence assertion