Why the tax rate manually entered at the AR line level is not picked in the AR Invoice header level

Summary:

Tax rate entered manually at the AR invoice line level are getting picked at the AR Invoice header level

Content (please ensure you mask any confidential information):

Hi Team,

We have an issue with tax defaulting for our client.

When we manually enter a tax rate in the Tax Classification field at the AR invoice line level and save it, the tax details in the header region pick a different tax rate or default to the one set by the tax rule.

How can we override the tax rule's tax rate in the header with the manually entered tax rate at the AR invoice line level?