diff --git a/purchase.py b/purchase.py
index 8b6b579207..15299ee410 100644
--- a/purchase.py
+++ b/purchase.py
@@ -92,9 +92,6 @@ class Purchase(OSV):
 
     def __init__(self):
         super(Purchase, self).__init__()
-        self._rpc_allowed += [
-            'button_compute',
-        ]
 
     def default_payment_term(self, cursor, user, context=None):
         payment_term_obj = self.pool.get('account.invoice.payment_term')
@@ -398,9 +395,6 @@ class Purchase(OSV):
         return super(Purchase, self).copy(cursor, user, purchase_id,
                 default=default, context=context)
 
-    def button_compute(self, cursor, user, ids, context=None):
-        pass
-
     def set_reference(self, cursor, user, purchase_id, context=None):
         sequence_obj = self.pool.get('ir.sequence')
 
diff --git a/purchase.xml b/purchase.xml
index 34507a7181..43c0d57ecf 100644
--- a/purchase.xml
+++ b/purchase.xml
@@ -52,22 +52,16 @@
                                 <label name="packing_state"/>
                                 <field name="packing_state"/>
                             </group>
-                            <group col="4" colspan="2">
-                                <label colspan="2"/>
+                            <group col="2" colspan="2">
                                 <label name="untaxed_amount"/>
                                 <field name="untaxed_amount"/>
-                                <label colspan="2"/>
                                 <label name="tax_amount"/>
                                 <field name="tax_amount"/>
-                                <button name="button_compute" string="Compute"
-                                    type="object" colspan="2"
-                                    states="{'readonly': '''state != 'draft' '''}"/>
                                 <label name="total_amount"/>
                                 <field name="total_amount"/>
-                                <label colspan="2"/>
                                 <label name="state"/>
                                 <field name="state"/>
-                                <group col="6" colspan="4">
+                                <group col="6" colspan="2">
                                     <button name="quotation" string="Quotation"
                                         states="{'invisible': '''state != 'draft' '''}"/>
                                     <button name="draft" string="Draft"