56% Tax on Rental Property Income!

My tax affairs are relatively simple, I have a full time job and a single rental property. My calculation for 23-24 shows a Profit from UK Land & Property as £795. I'm just in the 40% tax bracket with my job, so I would expect the tax liability to be 40% of £795 or around £320. My self assessment calculation however insists that I actually owe £446, which works out around 55%. It's very confusing and I think I asked the same question last year without getting a reply I could understand!

Hi,
Unfortunately, it is not possible to review personal matters in this forum. For individualised assistance please contact our Self Assessment team for advice: 
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Thank you.
 

You're assuming that the amount due after Self Assessment is entirely attributable to your income from property - but given what you've said, that sounds like it isn't the case. It's important to bear in mind that tax paid as you earn is sometimes more of a best effort estimate than a correct value, and the Self Assessment goes back over all your tax matters for the year to true things up. If you're doing your tax return on the gov.uk website, try going to "View your calculation" and then "View and print your full calculation" - the full calculation provides detailed information on how the website came up with the number it did. Compare the tax the full calculation deems applicable to your employment income, with the amount of tax already deducted from it (from your P60). There's a good chance you'll find the extra pounds accounted for in a difference there.