diff --git a/erpnext/erpnext_integrations/doctype/plaid_settings/plaid_connector.py b/erpnext/erpnext_integrations/doctype/plaid_settings/plaid_connector.py
index 66d0e5f77db..5f990cdd034 100644
--- a/erpnext/erpnext_integrations/doctype/plaid_settings/plaid_connector.py
+++ b/erpnext/erpnext_integrations/doctype/plaid_settings/plaid_connector.py
@@ -20,7 +20,7 @@ class PlaidConnector():
 			client_id=self.settings.plaid_client_id,
 			secret=self.settings.get_password("plaid_secret"),
 			environment=self.settings.plaid_env,
-			api_version="2019-05-29"
+			api_version="2020-09-14"
 		)
 
 	def get_access_token(self, public_token):
@@ -29,7 +29,7 @@ class PlaidConnector():
 		response = self.client.Item.public_token.exchange(public_token)
 		access_token = response["access_token"]
 		return access_token
-	
+
 	def get_token_request(self, update_mode=False):
 		country_codes = ["US", "CA", "FR", "IE", "NL", "ES", "GB"] if self.settings.enable_european_access else ["US", "CA"]
 		args = {
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
diff --git a/requirements.txt b/requirements.txt
index 4511aa54d8d..5a352364b6e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,7 +3,7 @@ frappe
 gocardless-pro==1.11.0
 googlemaps==3.1.1
 pandas>=1.0.5
-plaid-python==6.0.0
+plaid-python>=7.0.0
 pycountry==19.8.18
 PyGithub==1.44.1
 python-stdnum==1.12
@@ -12,4 +12,4 @@ taxjar==1.9.0
 tweepy==3.8.0
 Unidecode==1.1.1
 WooCommerce==2.1.1
-pycryptodome==3.9.8
\ No newline at end of file
+pycryptodome==3.9.8