Steps to reproduce: - Create a request for quotation for a product with set vendor Taxes - Create an alternative purchase order from that RFQ with Copy Product Current Behavior: The purchase order line of the PO associated with the created alternative does not compute the taxes. Expected behavior: The taxes should be computed in the same way as if the PO was created manually and then linked to the alternatives. Cause of the issue: When creating a PO manually, the taxes of each purchase order line are computed when the product is set during the call of the `onchange_product_id` onchange method: https://github.com/odoo/odoo/blob/64c13193ae0fe23eb1b426f5bbcd8531e9a40967/addons/purchase/models/purchase.py#L1221 https://github.com/odoo/odoo/blob/7ed0a773b6e0711b127f236ce665c35202d973bc/addons/purchase/models/purchase.py#L1055-L1061 By contrast, PO created from the `action_create_alternative` generate each `purchase.order.line` using `Command.create`. Therefore these lines will not trigger the onchange method and their taxes will not be computed. Fix: To KISS, we compute the taxes of each line just after the creation of the record using the `_compute_tax_id` method. opw-3750719 closes odoo/odoo#158300 X-original-commit: 15799594bda41bdb4b65387aa5f0d46482cb91c1 Signed-off-by: William Henrotin (whe) <whe@odoo.com>