Final answer:
Prenumbered documents will only be useful for control purposes if the sequence is accounted for periodically, to ensure that all documents are used and to detect any missing ones.
Step-by-step explanation:
Prenumbered documents are an important internal control mechanism that companies use to prevent errors and fraud. They help in tracking and recording transactions systematically. For prenumbered documents to be useful for control purposes, the sequence must be accounted for periodically. This means that there should be checks in place to ensure that every document in the sequence is used and accounted for, and any missing documents are investigated. Permitting documents to be used out of sequence or having varying sequences for each company diminishes the effectiveness of this control measure. Using the same numerical sequence each accounting period doesn't inherently increase the control effectiveness, unless coupled with regular sequence checks.