Updating Tax Rates for a Specific Line Item in an Existing WooCommerce Order

I’m working on a challenge where I have to update the tax rate for a specific line item in an existing WooCommerce order based on its SKU. I realize that the method I’m using may not be the best practice, but due to some constraints in my workflow, this is the approach I’ve had to take. Specifically, I aim to change the tax rate from a standard rate to a reduced rate, while retaining the original tax amount.

I’ve succeeded in eliminating the standard tax rate and replacing it with the reduced one. However, the problem arises when trying to retain the original tax amount within the line item after these changes. Clicking "Recalculate" in the WooCommerce dashboard resets the tax back to the standard rate.

Has anyone faced a similar issue or have suggestions to fix this while working within my constraints?

Thank you!

Here is what I’ve been trying so far:

add_action('init', 'update_order_tax_rate');

function update_order_tax_rate() {
    if (isset($_GET['run_my_script']) && $_GET['run_my_script'] == 'true') {
        $order_id = 79556;
        $order = wc_get_order($order_id);

        if (!$order) {
            return;
        }

        // Eliminar la tasa de impuestos anterior
        $taxes = $order->get_taxes();
        foreach ($taxes as $tax) {
            if ($tax->get_rate_code() == 'ES-IVA-1') {
                $order->remove_item($tax->get_id());
            }
        }

        // Añadir nueva tasa de impuestos
        $item = new WC_Order_Item_Tax();
        $item->set_rate(9); // El ID de la tasa de impuesto que quieres aplicar
        $item->set_order_id($order_id);
        $item->save();
        $order->add_item($item);

        // Actualizar el impuesto del ítem con el SKU especificado
        foreach ($order->get_items() as $item_id => $item) {
            $sku = $item->get_meta('SKU'); // Suponiendo que 'SKU' es el metakey
            if ($sku === 'HIB-1000') {
                $subtotal = $item->get_subtotal();
                $new_tax_amount = $subtotal * 0.1;
                $item->update_meta_data('_line_tax', wc_format_decimal($new_tax_amount));
                $item->save();
            }
        }

        $order->save();
    }
}

I’ve tried a variety of approaches to solve this issue. First, I attempted to directly change the tax rate ID on the specific line item, expecting the change to take effect immediately. However, the rate did not change.

Then, I tried removing the existing tax rate and adding a new one with the desired reduced rate. My expectation was that the new tax rate would apply correctly to the specific line item, but this didn’t happen either.

Furthermore, when I click on "Recalculate" in the WooCommerce dashboard, the tax rate reverts back to the standard rate, which is not the desired outcome.

So, essentially, while I can get close to a solution, I haven’t yet been able to make the change stick, specifically for the line item in question.