Meaning/Usage: To be very thankful
Explanation: This is commonly used when you feel that simply saying thank you is not enough. If someone did something very special for you, then you are expressing that no words can repay what they did. So this phrase is used to convey this message.
"I can't thank you enough for all that you have done for me."
"Thanks for everything. I can't thank you enough."
"You were a big help today watching the kids. I can't thank you enough."
A. "So how is your car running since I worked on it?"
B. "It is running great! I can't thank you enough. You were such a big help!"
Other Common Sentences
"I really appreciate all that you have done."
"Thank you very much!"