have yet to doは完了系の文章ですか？現在形ですか？？ →　意味は現在完了の否定で、形の上では現在形です。
Many of the suppliers [have(現在) yet to submit] invoices for services received in December.
＝ Many of the suppliers [have not yet submitted](現在完了・否定) invoices for services received in December.

参考にしてください。