SQL Server- SUM Subquery each other - sql

Question

I would like to ask for a little help in SQL Server.
How can I sum each other subquery and display it into one column.
I tested to add the subqueries in the SELECT statement, but, then I realize that I don't know how to sum between them, then I added them to the FROM statement to see If I adding them up in the SELECT statement could but work, but it didn't.
the idea is to substract B with A for each CodUbic.
'A' for purchases ($),
'B' for returned products ($)
SELECT
MONTH(FechaE) AS Mes,
YEAR(FechaE) AS Ano,
CodUbic,
TipoFac,
(SumFacA + SumFacB)
FROM
dbo.SAFACT,
(SELECT SUM(Monto) FROM dbo.SAFACT WHERE TipoFac IN ('A')) AS SumFacA,
(SELECT -SUM(Monto) FROM dbo.SAFACT WHere TipoFac IN ('B')) AS SumFacB
WHERE
TipoFac IN ('A', 'B')
GROUP BY
MONTH(FechaE),
YEAR(FechaE),
CodUbic,
TipoFac
ORDER BY
YEAR(FechaE) DESC,
MONTH(FechaE);
Expected Result:
Mes Ano CodUbic TotalSum
----------------------------------------------------
1 2022 0002-1 #### (Due the sum of A-B)
1 2022 0004-1 #### (Due the sum of A-B)
2 2022 0002-1 #### (Due the sum of A-B)
2 2022 0004-1 #### (Due the sum of A-B)
... ... ... ...

Answer 1

You are finally showing the expected result. It doesn't contain a column for TipoFac. This means, you want a result row per month and CodUbic, not per month, CodUbic, and TipoFac. Change your GROUP BY clause accordingly.
You get the difference between A and B with conditional aggregation (CASE WHEN inside the aggregation function).
SELECT
MONTH(FechaE) AS Mes, YEAR(FechaE) AS Ano, CodUbic,
SUM(CASE WHEN TipoFac = 'A' THEN monto ELSE -monto END) AS diff
FROM
dbo.SAFACT
WHERE
TipoFac IN ('A', 'B')
GROUP BY
MONTH(FechaE), YEAR(FechaE), CodUbic
ORDER BY
YEAR(FechaE) DESC, MONTH(FechaE), CodUbic
;

Answer 2

Simply:
SELECT
MONTH(FechaE) AS Mes,
YEAR(FechaE) AS Ano,
CodUbic,
SUM(CASE WHEN TipoFac = 'A' THEN ISNULL(Monto,0) ELSE 0 END) -
SUM(CASE WHEN TipoFac = 'B' THEN ISNULL(Monto,0) ELSE 0 END)
FROM
dbo.SAFACT
WHERE
TipoFac IN ('A', 'B')
GROUP BY
MONTH(FechaE),
YEAR(FechaE),
CodUbic
ORDER BY
YEAR(FechaE) DESC,
MONTH(FechaE);