完了不定詞継続は、継続していたが今は完了した行動を表し、動詞の後に続きます。完了不定詞継続の形状：
to have been + 現在分詞
現在不定詞と同様に、toなしの完了不定詞継続が必要な場合があり、その場合は toをなくします。これはほとんどの法助動詞の後やtoなし不定詞が使われる所で起こります。
例
- The woman seemed to have been crying.
- He pretended to have been painting all day.
- I would have preferred to have been sleeping all afternoon.
- You must have been waiting for hours!
- They might have been talking before you came in.
- You should have been studying for your test.