Taxation of dividend income- possible HMRC error?

Wonder if HMRC can help please? When checking this tax year's tax calculations (22/23) I noticed what seemed an anomaly. My Pension plus Employment plus Savings Interest did not use the whole amount of my Basic Tax Band of £37,700 (after deducting personal Allowance of £12,570). So I expected the 1st part of my remaining income - the Dividend Income stream - to be taxed at basic rate of 8.75% (after deducting the £2,000 dividend allowance), with the rest taxed at 33.75%. However, I found that all my income streams had been added together at the start of computation, then the amount of £37,700 entirely taxed at 20%, then the £500 savings allowance and £2,000 dividend allowance deducted, before taxing the rest of the dividend income all at 33.75%. This means that, rather than taxing the 1st part of Dividend Income stream (amounting to £2773) at 8.75%, it was in fact taxed at 20%, before proceeding to tax the remainder at 33.75%. I then noticed the same thing had happened last Tax Year (21/22), though the earlier Tax Years were correct because the entire £37,700 band was utilised by salary plus pensions plus savings, before needing to address the Dividend Income. Can HMRC confirm this to be an anomaly please, and how can I go about addressing this situation? Thank you. 

Name removed admin .

Hi Sal Unclear,
You will need to contact HMRC to review the calculations:
Contact HMRC
Thank you.