diff --git a/erpnext/regional/doctype/lower_deduction_certificate/lower_deduction_certificate.py b/erpnext/regional/doctype/lower_deduction_certificate/lower_deduction_certificate.py
index e8a8ed87505..ad60db05595 100644
--- a/erpnext/regional/doctype/lower_deduction_certificate/lower_deduction_certificate.py
+++ b/erpnext/regional/doctype/lower_deduction_certificate/lower_deduction_certificate.py
@@ -5,12 +5,16 @@
 from __future__ import unicode_literals
 import frappe
 from frappe import _
-from frappe.utils import getdate
+from frappe.utils import getdate, get_link_to_form
 from frappe.model.document import Document
 from erpnext.accounts.utils import get_fiscal_year
 
 class LowerDeductionCertificate(Document):
 	def validate(self):
+		self.validate_dates()
+		self.validate_supplier_against_section_code()
+		
+	def validate_dates(self):
 		if getdate(self.valid_upto) < getdate(self.valid_from):
 			frappe.throw(_("Valid Upto date cannot be before Valid From date"))
 
@@ -24,3 +28,20 @@ class LowerDeductionCertificate(Document):
 			<= fiscal_year.year_end_date):
 			frappe.throw(_("Valid Upto date not in Fiscal Year {0}").format(frappe.bold(self.fiscal_year)))
 
+	def validate_supplier_against_section_code(self):
+		duplicate_certificate = frappe.db.get_value('Lower Deduction Certificate', {'supplier': self.supplier, 'section_code': self.section_code}, ['name', 'valid_from', 'valid_upto'], as_dict=True)
+		if duplicate_certificate and self.are_dates_overlapping(duplicate_certificate):
+			certificate_link = get_link_to_form('Lower Deduction Certificate', duplicate_certificate.name)
+			frappe.throw(_("There is already a valid Lower Deduction Certificate {0} for Supplier {1} against Section Code {2} for this time period.")
+				.format(certificate_link, frappe.bold(self.supplier), frappe.bold(self.section_code)))
+
+	def are_dates_overlapping(self,duplicate_certificate):
+		valid_from = duplicate_certificate.valid_from
+		valid_upto = duplicate_certificate.valid_upto
+		if valid_from <= getdate(self.valid_from) <= valid_upto:
+			return True
+		elif valid_from <= getdate(self.valid_upto) <= valid_upto:
+			return True
+		elif getdate(self.valid_from) <= valid_from and valid_upto <= getdate(self.valid_upto):
+			return True
+		return False
\ No newline at end of file