diff --git a/api-specs/api/types/cart/LineItemDraft.raml b/api-specs/api/types/cart/LineItemDraft.raml
index 84a1ba23b..62435a743 100644
--- a/api-specs/api/types/cart/LineItemDraft.raml
+++ b/api-specs/api/types/cart/LineItemDraft.raml
@@ -63,7 +63,7 @@ properties:
   externalTaxRate?:
     type: ExternalTaxRateDraft
     description: |
-      Sets the external Tax Rate for the Line Item, if the Cart has the `External` [TaxMode](ctp:api:type:TaxMode).
+      Sets the external Tax Rate for the Line Item, if the Cart has the `External` [TaxMode](ctp:api:type:TaxMode) and `Single` [ShippingMode](ctp:api:type:ShippingMode).
   perMethodExternalTaxRate?:
     type: MethodExternalTaxRateDraft[]
     description: |
diff --git a/api-specs/api/types/cart/updates/CartAddLineItemAction.raml b/api-specs/api/types/cart/updates/CartAddLineItemAction.raml
index ed800b320..6a28ef57f 100644
--- a/api-specs/api/types/cart/updates/CartAddLineItemAction.raml
+++ b/api-specs/api/types/cart/updates/CartAddLineItemAction.raml
@@ -76,7 +76,7 @@ properties:
   externalTaxRate?:
     type: ExternalTaxRateDraft
     description: |
-      External Tax Rate for the Line Item, if the Cart has the `External` [TaxMode](ctp:api:type:TaxMode).
+      External Tax Rate for the Line Item, if the Cart has the `External` [TaxMode](ctp:api:type:TaxMode) and `Single` [ShippingMode](ctp:api:type:ShippingMode).
   perMethodExternalTaxRate?:
     type: MethodExternalTaxRateDraft[]
     description: |