diff --git a/bpfin/back_end_call/back_end_inputs.py b/bpfin/back_end_call/back_end_inputs.py
index 8c7b283f7a7f4acd5a202ea5616adbe249c79c3c..65a7f4a8963b6f49757e3a51d107a007d163e07b 100644
--- a/bpfin/back_end_call/back_end_inputs.py
+++ b/bpfin/back_end_call/back_end_inputs.py
@@ -18,9 +18,10 @@ def form_annual_bill_table(raw_monthly_bill_table, raw_annual_bill_table, analys
         raw_annual_bill_table (dictionary): dictionary of dictionary of annual bills, at lease 0 year data is required
 
     Returns:
-        list: list of lists, display prior_annual_bill and manual_input indicators in displaying formatting
         bill_overview_dict (dictionary): dictionary of dictionary of annual bills, see description for detail
-        # manual_input_dict (dictionary): dictionary of boolean values, keys are utilities
+        manual_input_dict (dictionary): this return is not used anywhere else, it's a placeholder
+        prior_month_bill_dict (dictionary): dictionary of dictionary, keys are utilities, see description for detail
+        bill_overview_instance (dictionary): dictionary of dictionaries, see description for API detail
 
     Error Validate:
         raw_monthly_bill_table, analysis_date == None, Raise empty error
@@ -56,6 +57,30 @@ def form_annual_bill_table(raw_monthly_bill_table, raw_annual_bill_table, analys
             'oil': dict of oil_bill,
             'gas': dict of gas_bill,
             'water': dict of water_bill}
+        prior_month_bill_dict = {
+            'electric': {
+                'date_from': list, prior_bill_start, month by month,
+                'date_to': list, prior_bill_end, month by month,
+                'usage': list of float,prior_monthly_usage,
+                'charge': list of float,prior_monthly_charge,
+                'price': list of float,prior_monthly_price},
+            'gas': same,
+            'oil': same,
+            'water': same}
+        bill_overview_instance = {
+            "instance":
+            {
+                "electric":{"2012": 44497.03, "2013": 45283.79, ... "2036": 70045.62},
+                "gas":{"2012": 10847.97, "2013": 11045.45, ... "2036": 17077.7},
+                "oil":{"2012": null, ... "2036": null},
+                "water":{"2012": null, ... "2036": null},
+                "electric_user": 'Annual Estimate',
+                "gas_user": 'Monthly Bill',
+                "oil_user": 'Not Available',
+                "water_user": 'Annual Estimate',
+                "total_annual_charge": {"2012": 55345.0, "2013": 56329.240000000005, ... "2036": 87123.31999999999}
+            }
+        }
 
     To Do: from utilbills.bill.py merge form_prior_month_bill(), and delete that one
             * this work is done. need all units test and then can delete that
@@ -87,23 +112,20 @@ def form_annual_bill_table(raw_monthly_bill_table, raw_annual_bill_table, analys
         raise ValueError('Bill_Overview - monthly_bill has incomplete result of monthly_proj')
 
     # formatting annual bill (bill overview on front end)
-    proforma_year = sorted(bill_overview_dict[UTILITY_TYPE_LIST[0]])
-    bill_overview_front_end_list = []
-
-    bill_overview_front_end_list.append(['Data Source', 'Utility/Year'])
-    bill_overview_front_end_list[0] += proforma_year
-
+    instance = {}
     for utility in UTILITY_TYPE_LIST:
-        utility_expense_list = []
-        utility_expense_list.append('Annual Estimate' if manual_input_dict[utility] else 'Monthly Bill')
-        utility_expense_list.append(utility)
-        utility_expense_list += [bill_overview_dict[utility][year] for year in proforma_year]
-        bill_overview_front_end_list.append(utility_expense_list)
+        # assign 4 annual bills under proforma years to instance. keys are 4 utilities
+        instance[utility] = bill_overview_dict[utility]
+        # assign 4 user input type to instance.
+        utility_user = utility + '_user'
+        instance[utility_user] = 'Annual Estimate' if manual_input_dict[utility] else 'Monthly Bill'
+    # assign total charge to instance. UI display: "Total Energy Expense"
+    instance["total_annual_charge"] = sum_energy_opex(bill_overview_dict)[0]
 
-    bill_overview_front_end_list.append(['', 'Total Energy Expense'])
-    bill_overview_front_end_list[-1] += sum_energy_opex(bill_overview_dict)[1]
+    bill_overview_instance = {"instance":instance}
+    # print('\ninstance = ', bill_overview_instance)
 
-    return bill_overview_dict, manual_input_dict, prior_month_bill_dict, bill_overview_front_end_list
+    return bill_overview_dict, manual_input_dict, prior_month_bill_dict, bill_overview_instance
 
 
 def form_prior_income_table(
@@ -171,10 +193,11 @@ def form_prior_income_table(
 # from bpfin.financials.liability import final_liability_dict
 # from bpfin.financials.financial_balance import Balance_Sheet_Table
 # from bpfin.tests.testdata import feature_data as db
-# print('\nannual_bill =', form_annual_bill_table(db.raw_monthly_bill_table, db.raw_annual_bill_table, db.analysis_date)[-1])
 
 # pp = pprint.PrettyPrinter(width=120, indent=4, compact=True)
-# pp.pprint(form_annual_bill_table(db.raw_monthly_bill_table, db.raw_annual_bill_table, db.analysis_date)[-1])
+# pp.pprint(form_annual_bill_table(db.raw_monthly_bill_table, db.raw_annual_bill_table, db.analysis_date)[1])
+
+# print('\nannual_bill =', form_annual_bill_table(db.raw_monthly_bill_table, db.raw_annual_bill_table, db.analysis_date)[-1])
 
 # print('\nprior_income_statement =', form_prior_income_table(
 #     db.raw_income_input,