battery size has to be entered where?
BTW they said they will mail explanation
Per my Tax and Financial Planner with whom I have had a long relationship and trust implicitly, there is no place on Form 8936 to enter battery size. If you go to the instructions for line 4a, you should have entered $7,500 since the Clarity meets the conditions of at least a 4 kW battery and GVW <14,000 lbs.
instructions here:
https://www.irs.gov/instructions/i8936
Honda has already provided the IRS with the information that the Clarity meets the standards for the full $7,500 credit and the IRS has accepted that.
Information on pertinent IRS Code Section 30D available here:
https://www.irs.gov/businesses/irc-30d-new-qualified-plug-in-electric-drive-motor-vehicle-credit
So your preparer should have entered the correct information on lines 1 through 4 and you should get the full credit.
You need to check that the correct Year/make/ model, VIN, date placed in service, $7,500, and 100% Phaseout percentage were entered.
Then you get the full credit if and only if line 11 (line 45 for 1040NR) from your 1040 (minus personal credits, see instructions) is => $7,500.
Full disclosure: I am not an accountant nor certified tax preparer and do not claim to be. Just trying to help you figure it out with the information you provided.
Please check your Form 8936 and let us know if it was filled out correctly and what the forthcoming IRS letter says.
Best of luck to you.