Self assessment calculation doesn't seem correct

I've completed my self assessment calculation for 22/23 however I feel the tax amount is incorrect. Self assessment website says I'm due £8K back, however my calculations and those of third party sites listentotaxman and uktaxcalculators all calculate it to be around 12k. There's nothing due from period years. I had made additional contributions towards my pension in March using the carry forward rules to bring me under the the 100K personal allowance tapering, I'm anticipating the mid-March is related to this somehow, What's the best course of action? Submit the assessment, perhaps leave a comment on it hoping someone will look at it, and then call self assessment helpline next week?

Hi,

Yes, you would need to submit it and then call so that your record can be accessed for it to be looked at.

Thank you.