The document's items are not right (VAT, rounding, missing part)
The incorrect tax rate on the invoice
If the tax rate on the invoice is not valid, please review your WooCommerce tax rates. Also, please edit this particular invoice and check the chosen tax rate:
Incorrect rounding on the invoice
Make sure that you have the Number of decimals option is set to 2 in your WooCommerce settings:
Read more on setting taxes in the How to Configure WooCommerce Taxes Complete Tutorial.