diff --git a/erpnext/public/js/controllers/transaction.js b/erpnext/public/js/controllers/transaction.js
index 78776a3..274e295 100644
--- a/erpnext/public/js/controllers/transaction.js
+++ b/erpnext/public/js/controllers/transaction.js
@@ -417,6 +417,16 @@
 	},
 
 	currency: function() {
+		/* cksgb 19/09/2016: We need to detect if this transaction is a PO/SO. 
+		If so, use transaction_date. 
+		If not, use posting_date as we assume that any other document type is an accounting document. */
+		
+		if (this.frm.doc.doctype == "Purchase Order" || this.frm.doc.doctype == "Sales Order"){
+			lookup_date = this.frm.doc.transaction_date;
+		}else{
+			lookup_date = this.frm.doc.posting_date;
+		}
+		
 		var me = this;
 		this.set_dynamic_labels();
 
@@ -424,7 +434,7 @@
 		// Added `ignore_pricing_rule` to determine if document is loading after mapping from another doc
 		if(this.frm.doc.currency && this.frm.doc.currency !== company_currency
 				&& !this.frm.doc.ignore_pricing_rule) {
-			this.get_exchange_rate(this.frm.doc.posting_date, this.frm.doc.currency, company_currency,
+			this.get_exchange_rate(lookup_date, this.frm.doc.currency, company_currency,
 				function(exchange_rate) {
 					me.frm.set_value("conversion_rate", exchange_rate);
 				});