My quick Google search for "I cannot thank you enough." returned a lot more results than for "I could not thank you enough."
- I cannot thank you enough. (6,030,000 results)
- I could not thank you enough. (448,000 results)
My questions are:
- Is "I could not thank you enough." just the past tense of "I cannot thank you enough."?
- If the answer for the above is No, then when do you use "I could not thank you enough." rather than "I cannot thank you enough."?
Best Answer
Could (like would) has two different uses.
So
with past meaning, is a straightforward past tense of I can't thank you enough.
With present meaning, it would probably be interpreted as something like
In that sense it sounds very effusive and over the top, and is much less common than "I can't thank you enough".