Answer:
The corrected sentence is:
"After you complete the application, you must turn the forms to the office."
Step-by-step explanation:
When there is an inappropriate shift of verb voice or mood, it means that the verb voice shifted from active to passive or from passive to active. Such shift can confuse the reader. So, when correcting the inappropriate verb voice, it's preferable to use the active voice. Also, whenever the subject of a sentence performs the action, it is known to be in the active voice. While if the subject receives the action, the sentence is in the passive voice.