Despite repeated reminders, the department has not acknowledged receipt of the relevant documents.

has + not + acknowledged 为现在完成时的完整否定。has 为单数助动词，not 置于助动词与过去分词之间构成正式否定，acknowledged 为过去分词，表示尽管多次提醒仍未确认的状态。适用于机构间的正式文书往来。