diff --git a/setup/doctype/company/company.js b/setup/doctype/company/company.js
index dfe8e2a..4859464 100644
--- a/setup/doctype/company/company.js
+++ b/setup/doctype/company/company.js
@@ -17,6 +17,10 @@
 cur_frm.cscript.refresh = function(doc, cdt, cdn) {
 	if(doc.abbr && !doc.__islocal)
 		cur_frm.set_df_property("abbr", "read_only", 1)
+		
+	if(!doc.__islocal) {
+		cur_frm.toggle_enable("default_currency", !cur_frm.doc.__transactions_exist);
+	}
 }
 
 cur_frm.cscript.has_special_chars = function(t) {
diff --git a/setup/doctype/company/company.py b/setup/doctype/company/company.py
index 8a10587..ee432c0 100644
--- a/setup/doctype/company/company.py
+++ b/setup/doctype/company/company.py
@@ -29,10 +29,30 @@
 	def __init__(self,d,dl):
 		self.doc, self.doclist = d,dl
 		
+	def onload(self):
+		self.doc.fields["__transactions_exist"] = self.check_if_transactions_exist()
+		
+	def check_if_transactions_exist(self):
+		exists = False
+		for doctype in ["Sales Invoice", "Delivery Note", "Sales Order", "Quotation",
+			"Purchase Invoice", "Purchase Receipt", "Purchase Order", "Supplier Quotation"]:
+				if webnotes.conn.sql("""select name from `tab%s` where company=%s and docstatus=1
+					limit 1""" % (doctype, "%s"), self.doc.name):
+						exists = True
+						break
+		
+		return exists
+		
 	def validate(self):
 		if self.doc.fields.get('__islocal') and len(self.doc.abbr) > 5:
 			webnotes.msgprint("Abbreviation cannot have more than 5 characters",
 				raise_exception=1)
+				
+		self.previous_default_currency = webnotes.conn.get_value("Company", self.doc.name, "default_currency")
+		if self.doc.default_currency and self.previous_default_currency and \
+			self.doc.default_currency != self.previous_default_currency and \
+			self.check_if_transactions_exist():
+				msgprint(_("Sorry! You cannot change company's default currency, because there are existing transactions against it. You will need to cancel those transactions if you want to change the default currency."), raise_exception=True)
 
 	def on_update(self):
 		if not webnotes.conn.sql("""select name from tabAccount