fix: calculate wdv depr schedule properly for existing assets [v13] (#35615)

* fix: calculate wdv depr schedule properly for existing assets

* fix: calculate wdv depr schedule properly for existing assets properly

erpnext/assets/doctype/asset/asset.py

@@ -27,6 +27,7 @@ from erpnext.accounts.general_ledger import make_reverse_gl_entries
 from erpnext.assets.doctype.asset.depreciation import (
 	get_depreciation_accounts,
 	get_disposal_account_and_cost_center,
+	is_first_day_of_the_month,
 	is_last_day_of_the_month,
 )
 from erpnext.assets.doctype.asset_category.asset_category import get_asset_category_account
@@ -364,8 +365,14 @@ class Asset(AccountsController):
 					break
 
 				# For first row
-				if n == 0 and has_pro_rata and not self.opening_accumulated_depreciation:
-					from_date = add_days(self.available_for_use_date, -1)
+				if (
+					n == 0
+					and (has_pro_rata or has_wdv_or_dd_non_yearly_pro_rata)
+					and not self.opening_accumulated_depreciation
+				):
+					from_date = add_days(
+						self.available_for_use_date, -1
+					)  # needed to calc depr amount for available_for_use_date too
 					depreciation_amount, days, months = self.get_pro_rata_amt(
 						finance_book,
 						depreciation_amount,
@@ -374,10 +381,18 @@ class Asset(AccountsController):
 						has_wdv_or_dd_non_yearly_pro_rata,
 					)
 				elif n == 0 and has_wdv_or_dd_non_yearly_pro_rata and self.opening_accumulated_depreciation:
-					from_date = add_months(
-						getdate(self.available_for_use_date),
-						(self.number_of_depreciations_booked * finance_book.frequency_of_depreciation),
-					)
+					if not is_first_day_of_the_month(getdate(self.available_for_use_date)):
+						from_date = get_last_day(
+							add_months(
+								getdate(self.available_for_use_date),
+								((self.number_of_depreciations_booked - 1) * finance_book.frequency_of_depreciation),
+							)
+						)
+					else:
+						from_date = add_months(
+							getdate(add_days(self.available_for_use_date, -1)),
+							(self.number_of_depreciations_booked * finance_book.frequency_of_depreciation),
+						)
 					depreciation_amount, days, months = self.get_pro_rata_amt(
 						finance_book,
 						depreciation_amount,

erpnext/assets/doctype/asset/depreciation.py

@@ -8,6 +8,7 @@ from frappe.utils import (
 	add_months,
 	cint,
 	flt,
+	get_first_day,
 	get_last_day,
 	get_link_to_form,
 	getdate,
@@ -543,3 +544,9 @@ def is_last_day_of_the_month(date):
 	last_day_of_the_month = get_last_day(date)
 
 	return getdate(last_day_of_the_month) == getdate(date)
+
+
+def is_first_day_of_the_month(date):
+	first_day_of_the_month = get_first_day(date)
+
+	return getdate(first_day_of_the_month) == getdate(date)

erpnext/assets/doctype/asset/test_asset.py

@@ -686,14 +686,14 @@ class TestDepreciationMethods(AssetSetup):
 			number_of_depreciations_booked=1,
 			opening_accumulated_depreciation=50000,
 			expected_value_after_useful_life=10000,
-			depreciation_start_date="2030-12-31",
+			depreciation_start_date="2031-12-31",
 			total_number_of_depreciations=3,
 			frequency_of_depreciation=12,
 		)
 
 		self.assertEqual(asset.status, "Draft")
 
-		expected_schedules = [["2030-12-31", 33333.50, 83333.50], ["2031-12-31", 6666.50, 90000.0]]
+		expected_schedules = [["2031-12-31", 33333.50, 83333.50], ["2032-12-31", 6666.50, 90000.0]]
 
 		schedules = [
 			[cstr(d.schedule_date), d.depreciation_amount, d.accumulated_depreciation_amount]