SQL Server 2022

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ItemId	DatePhysical	Qty
1	2023-01-01	10
1	2023-01-01	5
1	2023-01-03	15
1	2023-01-03	10
1	2023-01-05	10
1	2023-01-05	5
2	2022-03-28	10
2	2022-01-31	20
2	2022-01-31	10
2	2023-01-02	15
2	2023-01-02	25
2	2023-01-02	30
2	2023-01-04	20
2	2023-01-04	15
2	2023-01-04	25

With  Inventory AS (
    SELECT ItemId, DatePhysical, SUM(Qty) AS TotalQuantity
    FROM Inventrans
    WHERE DatePhysical <= '2023-01-07'
    GROUP BY ItemId, DatePhysical
), StartingInventory AS (
    SELECT ItemId,DatePhysical='2023-01-01',SUM(Qty) AS StartingQuantity
    FROM Inventrans
    WHERE DatePhysical < '2023-01-01'
    GROUP BY ItemId
),AllDates as(
    select DatePhysical=cast('2023-01-01' as date)
    UNION ALL
    SELECT dateadd(day,1,[DatePhysical]) from AllDates where DatePhysical<'2023-01-07'
), AllIDDate as(
select distinct itemid,j.DatePhysical from Inventory i cross apply AllDates j 
)

select j.ItemId,j.DatePhysical,coalesce(sum(i.TotalQuantity) over (partition by j.itemId order by j.DatePhysical),0)+ 
COALESCE(s.StartingQuantity, 0) AS DailyTotalInventory
from AllIDDate j 
LEFT JOIN Inventory i on i.ItemId = j.ItemId and i.DatePhysical=j.DatePhysical
LEFT JOIN StartingInventory s ON j.ItemId = s.ItemId and j.DatePhysical=s.DatePhysical
WHERE j.DatePhysical BETWEEN '2023-01-01' AND '2023-01-07'

ItemId	DatePhysical	DailyTotalInventory
1	2023-01-01	15
1	2023-01-02	15
1	2023-01-03	40
1	2023-01-04	40
1	2023-01-05	55
1	2023-01-06	55
1	2023-01-07	55
2	2023-01-01	40
2	2023-01-02	70
2	2023-01-03	70
2	2023-01-04	130
2	2023-01-05	130
2	2023-01-06	130
2	2023-01-07	130

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