SQL Server 2019

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DECLARE
    @FromDate DATE
  , @ToDate   DATE
  , @Supplier INT
  , @MOP      INT;

-- set these values to whatever you would pass to your store procedure
SET @FromDate = '2020-03-01';
SET @ToDate = '2020-03-31';
SET @Supplier = 2;
SET @MOP = 3;

DECLARE @Expenditure TABLE
(
    ID INT NOT NULL
  , TranDate DATE NOT NULL
  , SupplierID INT NOT NULL
  , MOP INT NOT NULL
  , NetAmount DECIMAL(10, 2) NOT NULL
);

INSERT INTO @Expenditure (ID, TranDate, SupplierID, MOP, NetAmount)
VALUES
  (1, '02/28/2020', 2, 3, 200.12)
, (2, '03/15/2020', 2, 3, 125.10)
, (3, '03/15/2020', 2, 3, 74.90)
, (4, '03/17/2020', 3, 3, 150.32)
, (5, '03/18/2020', 2, 3, 250.78)

;WITH cteCalendar (MyDate) AS
(
    SELECT CONVERT(DATE, @FromDate) AS MyDate
    UNION ALL
    SELECT DATEADD(DAY, 1, MyDate)
    FROM   cteCalendar
    WHERE  DATEADD(DAY, 1, MyDate) <= @ToDate
)
SELECT
     ROW_NUMBER() OVER (ORDER BY x.TranDate) AS [RowNo]
   , x.TranDate
   , x.NetExpense
FROM (
         SELECT
                   c.MyDate         AS TranDate
                 , SUM(e.NetAmount) AS [NetExpense]
         FROM      cteCalendar  c
         LEFT JOIN @Expenditure e ON c.MyDate = e.TranDate
                                     AND e.SupplierID = @Supplier
                                     AND e.MOP = @MOP
         GROUP BY  c.MyDate
     ) x;

RowNo	TranDate	NetExpense
1	2020-03-01	null
2	2020-03-02	null
3	2020-03-03	null
4	2020-03-04	null
5	2020-03-05	null
6	2020-03-06	null
7	2020-03-07	null
8	2020-03-08	null
9	2020-03-09	null
10	2020-03-10	null
11	2020-03-11	null
12	2020-03-12	null
13	2020-03-13	null
14	2020-03-14	null
15	2020-03-15	200.00
16	2020-03-16	null
17	2020-03-17	null
18	2020-03-18	250.78
19	2020-03-19	null
20	2020-03-20	null
21	2020-03-21	null
22	2020-03-22	null
23	2020-03-23	null
24	2020-03-24	null
25	2020-03-25	null
26	2020-03-26	null
27	2020-03-27	null
28	2020-03-28	null
29	2020-03-29	null
30	2020-03-30	null
31	2020-03-31	null

Warning: Null value is eliminated by an aggregate or other SET operation.