Tax calculation is wrong

The tax calculation of my shop is wrong. It should be 21% VAT, but the calculated VAT fee is always wrong. For example, when I put an article in the cart of €45 (VAT included), it displays on the cart and checkout page: ‘€45 (including €7,81 VAT)’, while it should be ‘€9,45 VAT’. I have set up the tax correctly in my settings though.

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