diff --git a/api/report-sales.php b/api/report-sales.php
index 34e4d870f..728aea551 100644
--- a/api/report-sales.php
+++ b/api/report-sales.php
@@ -60,23 +60,17 @@
                     CAST(ROUND_TO_EVEN(
                       SUM(IF(txn_line.taxfree, 1, 0) *
                         IF(type = 'customer', -1, 1) * ordered *
-                        CASE txn_line.discount_type
-                          WHEN 'percentage' THEN txn_line.retail_price * ((100 - txn_line.discount) / 100)
-                          WHEN 'relative' THEN (txn_line.retail_price - txn_line.discount) 
-                          WHEN 'fixed' THEN (txn_line.discount)
-                          ELSE txn_line.retail_price
-                        END),
+                        sale_price(txn_line.retail_price,
+                                   txn_line.discount_type,
+                                   txn_line.discount)),
                       2) AS DECIMAL(9,2))
                     AS untaxed,
                     CAST(ROUND_TO_EVEN(
                       SUM(IF(txn_line.taxfree, 0, 1) *
                         IF(type = 'customer', -1, 1) * ordered *
-                        CASE txn_line.discount_type
-                          WHEN 'percentage' THEN txn_line.retail_price * ((100 - txn_line.discount) / 100)
-                          WHEN 'relative' THEN (txn_line.retail_price - txn_line.discount) 
-                          WHEN 'fixed' THEN (txn_line.discount)
-                          ELSE txn_line.retail_price
-                        END),
+                        sale_price(txn_line.retail_price,
+                                   txn_line.discount_type,
+                                   txn_line.discount)),
                       2) AS DECIMAL(9,2))
                     AS taxed,
                     tax_rate
diff --git a/api/txn-list.php b/api/txn-list.php
index aaf7b7d9d..a84b7aefb 100644
--- a/api/txn-list.php
+++ b/api/txn-list.php
@@ -57,23 +57,13 @@
             CAST(ROUND_TO_EVEN(
               SUM(IF(txn_line.taxfree, 1, 0) *
                 IF(type = 'customer', -1, 1) * allocated *
-                CASE discount_type
-                  WHEN 'percentage' THEN retail_price * ((100 - discount) / 100)
-                  WHEN 'relative' THEN (retail_price - discount) 
-                  WHEN 'fixed' THEN (discount)
-                  ELSE retail_price
-                END),
+                sale_price(retail_price, discount_type, discount)),
               2) AS DECIMAL(9,2))
             untaxed,
             CAST(ROUND_TO_EVEN(
               SUM(IF(txn_line.taxfree, 0, 1) *
                 IF(type = 'customer', -1, 1) * allocated *
-                CASE discount_type
-                  WHEN 'percentage' THEN retail_price * ((100 - discount) / 100)
-                  WHEN 'relative' THEN (retail_price - discount) 
-                  WHEN 'fixed' THEN (discount)
-                  ELSE retail_price
-                END),
+                sale_price(retail_price, discount_type, discount)),
               2) AS DECIMAL(9,2))
             taxed,
             tax_rate,
diff --git a/export/sales.php b/export/sales.php
index c67af5dc0..88e15430a 100644
--- a/export/sales.php
+++ b/export/sales.php
@@ -26,23 +26,13 @@
             CAST(ROUND_TO_EVEN(
               SUM(IF(txn_line.taxfree, 1, 0) *
                 IF(type = 'customer', -1, 1) * allocated *
-                CASE discount_type
-                  WHEN 'percentage' THEN retail_price * ((100 - discount) / 100)
-                  WHEN 'relative' THEN (retail_price - discount) 
-                  WHEN 'fixed' THEN (discount)
-                  ELSE retail_price
-                END),
+                sale_price(retail_price, discount_type, discount)),
               2) AS DECIMAL(9,2))
             untaxed,
             CAST(ROUND_TO_EVEN(
               SUM(IF(txn_line.taxfree, 0, 1) *
                 IF(type = 'customer', -1, 1) * allocated *
-                CASE discount_type
-                  WHEN 'percentage' THEN retail_price * ((100 - discount) / 100)
-                  WHEN 'relative' THEN (retail_price - discount) 
-                  WHEN 'fixed' THEN (discount)
-                  ELSE retail_price
-                END),
+                sale_price(retail_price, discount_type, discount)),
               2) AS DECIMAL(9,2))
             taxed,
             tax_rate
diff --git a/lib/txn.php b/lib/txn.php
index 1d18f4d27..744e5cce7 100644
--- a/lib/txn.php
+++ b/lib/txn.php
@@ -44,23 +44,13 @@ function txn_load($db, $id) {
               CAST(ROUND_TO_EVEN(
                 SUM(IF(txn_line.taxfree, 1, 0) *
                   IF(type = 'customer', -1, 1) * ordered *
-                  CASE discount_type
-                    WHEN 'percentage' THEN retail_price * ((100 - discount) / 100)
-                    WHEN 'relative' THEN (retail_price - discount) 
-                    WHEN 'fixed' THEN (discount)
-                    ELSE retail_price
-                  END),
+                  sale_price(retail_price, discount_type, discount)),
                 2) AS DECIMAL(9,2))
               untaxed,
               CAST(ROUND_TO_EVEN(
                 SUM(IF(txn_line.taxfree, 0, 1) *
                   IF(type = 'customer', -1, 1) * ordered *
-                  CASE discount_type
-                    WHEN 'percentage' THEN retail_price * ((100 - discount) / 100)
-                    WHEN 'relative' THEN (retail_price - discount) 
-                    WHEN 'fixed' THEN (discount)
-                    ELSE retail_price
-                  END),
+                  sale_price(retail_price, discount_type, discount)),
                 2) AS DECIMAL(9,2))
               taxed,
               tax_rate,
@@ -88,22 +78,11 @@ function txn_load_items($db, $id) {
               txn_line.id AS line_id, item.code, item.id AS item_id,
               IFNULL(override_name, item.name) name, data,
               txn_line.retail_price msrp,
-              IF(txn_line.discount_type,
-                 CASE txn_line.discount_type
-                   WHEN 'percentage' THEN CAST(ROUND_TO_EVEN(txn_line.retail_price * ((100 - txn_line.discount) / 100), 2) AS DECIMAL(9,2))
-                   WHEN 'relative' THEN (txn_line.retail_price - txn_line.discount) 
-                   WHEN 'fixed' THEN (txn_line.discount)
-                 END,
-                 txn_line.retail_price) price,
+              sale_price(txn_line.retail_price, txn_line.discount_type,
+                         txn_line.discount) price,
               (IF(type = 'customer', -1, 1) * ordered *
-               CASE txn_line.discount_type
-                 WHEN 'percentage' THEN txn_line.retail_price *
-                                         ((100 - txn_line.discount) / 100)
-                 WHEN 'relative' THEN (txn_line.retail_price -
-                                       txn_line.discount) 
-                 WHEN 'fixed' THEN (txn_line.discount)
-                 ELSE txn_line.retail_price
-               END) AS ext_price,
+               sale_price(txn_line.retail_price, txn_line.discount_type,
+                          txn_line.discount)) AS ext_price,
               IFNULL(CONCAT(IF(item.retail_price, 'MSRP $', 'List $'),
                             txn_line.retail_price,
                             CASE txn_line.discount_type