diff --git a/src/clj/auto_ap/db/invoices.clj b/src/clj/auto_ap/db/invoices.clj
index 1baff022..35fcf95c 100644
--- a/src/clj/auto_ap/db/invoices.clj
+++ b/src/clj/auto_ap/db/invoices.clj
@@ -63,7 +63,7 @@
 (defn get-all []
   (query base-query))
 
-(defn find-conflicting [{:keys [id invoice-number company-id vendor-id]}]
+(defn find-conflicting [{:keys [id invoice-number company-id vendor-id] :as i}]
   (query
    (-> base-query
        (helpers/merge-where [:and [:not= :id id]
diff --git a/src/clj/auto_ap/graphql/invoices.clj b/src/clj/auto_ap/graphql/invoices.clj
index f743d063..ad246094 100644
--- a/src/clj/auto_ap/graphql/invoices.clj
+++ b/src/clj/auto_ap/graphql/invoices.clj
@@ -37,8 +37,14 @@
         (->graphql))))
 
 
-(defn edit-invoice [context {{:keys [id] :as in} :invoice} value]
+(defn edit-invoice [context {{:keys [id invoice_number vendor_id company_id] :as in} :invoice} value]
+  
   (let [invoice (invoices/get-by-id id)
+        _ (when (seq (invoices/find-conflicting {:id id
+                                                 :invoice-number invoice_number
+                                                 :vendor-id (:vendor-id invoice)
+                                                 :company-id (:company-id invoice)}))
+            (throw (ex-info "that invoice already exists" {:invoice-number invoice_number})))
         paid-amount (- (:total invoice) (:outstanding-balance invoice))
         _ (assert-can-see-company (:id context) (:company-id invoice))
         updated-invoice (invoices/update (-> in
diff --git a/src/cljs/auto_ap/views/pages/unpaid_invoices.cljs b/src/cljs/auto_ap/views/pages/unpaid_invoices.cljs
index 27190b92..006b4d28 100644
--- a/src/cljs/auto_ap/views/pages/unpaid_invoices.cljs
+++ b/src/cljs/auto_ap/views/pages/unpaid_invoices.cljs
@@ -279,7 +279,8 @@
                                                   [:expense_accounts [:amount :id :expense_account_id
                                                                       :location
                                                                       [:expense_account [:id :name [:parent [:id :name]]]]]]]]}]}  
-       :on-success [::invoice-edited]}})))
+       :on-success [::invoice-edited]
+       :on-error [::invoice-edit-failed]}})))
 
 
 (re-frame/reg-event-fx
@@ -361,6 +362,12 @@
                                   i)) is)))
             (dissoc ::edit-invoice))}))
 
+
+(re-frame/reg-event-fx
+ ::invoice-edit-failed
+ (fn [{:keys [db]} [_ data]]
+   {:dispatch [::events/modal-failed ::edit-invoice "That invoice already exists."]}))
+
 (re-frame/reg-event-fx
  ::invoice-voided
  (fn [{:keys [db]} [_ {:keys [void-invoice]}]]