You could have + (past participle)

Using 'could have' you are speaking about something that was, should be or would be. You are stating that they had other options that could have been chosen.

Here are some examples:

"You could have completed it sooner."
"You could have blown your chance."
"You could have done better on your exam."
"You could have given me more time to get ready."
"You could have heard that from someone else."
"You could have sent that package first class."
"You could have slept in a little longer."
"You could have written him a letter."
"You could have thought of something to do."
"You could have upset her by saying that."