fix: tax_item_rate calculation

erpnext/controllers/accounts_controller.py

@@ -3176,10 +3176,12 @@ def set_child_tax_template_and_map(item, child_item, parent_doc):
 	)
 
 	child_item.item_tax_template = _get_item_tax_template(ctx, item.taxes)
-	if child_item.get("item_tax_template"):
-		child_item.item_tax_rate = get_item_tax_map(
-			parent_doc.get("company"), child_item.item_tax_template, as_json=True
-		)
+	child_item.item_tax_rate = get_item_tax_map(
+		parent_doc.get("company"),
+		child_item.item_tax_template,
+		as_json=True,
+		parent_doc=parent_doc,
+	)
 
 
 def add_taxes_from_tax_template(child_item, parent_doc, db_insert=True):

erpnext/stock/get_item_details.py

@@ -101,6 +101,7 @@ def get_item_details(
 		ctx.company,
 		out.item_tax_template or ctx.item_tax_template,
 		as_json=True,
+		parent_doc=doc,
 	)
 
 	get_party_item_code(ctx, item, out)
@@ -689,10 +690,15 @@ def is_within_valid_range(ctx: ItemDetailsCtx, tax) -> bool:
 
 
 @frappe.whitelist()
-def get_item_tax_map(company, item_tax_template, as_json=True):
+def get_item_tax_map(company, tax_template=None, as_json=True, parent_doc: dict | Document | None = None):
 	item_tax_map = {}
-	if item_tax_template:
-		template = frappe.get_cached_doc("Item Tax Template", item_tax_template)
+	doctype = "Item Tax Template"
+	if not tax_template and parent_doc:
+		doctype = frappe.get_meta(parent_doc).get_link_doctype("taxes_and_charges")
+		tax_template = parent_doc.get("taxes_and_charges")
+
+	if doctype and tax_template:
+		template = frappe.get_cached_doc(doctype, tax_template)
 		for d in template.taxes:
 			if frappe.get_cached_value("Account", d.tax_type, "company") == company:
 				item_tax_map[d.tax_type] = d.tax_rate