SQL Server 2017

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CREATE TABLE [dbo].[tbl]
(
[CGSTPer] [DECIMAL](18, 2) NULL,
[CGSTAmt] [DECIMAL](18, 2) NULL,
[SGSTPer] [DECIMAL](18, 2) NULL,
[SGSTAmt] [DECIMAL](18, 2) NULL,
[IGSTPer] [DECIMAL](18, 2) NULL,
[IGSTAmt] [DECIMAL](18, 2) NULL,
[Id] [NUMERIC](18, 0) NOT NULL
)

INSERT INTO dbo.tbl
(CGSTPer,CGSTAmt,SGSTPer,SGSTAmt,IGSTPer,IGSTAmt,Id)
SELECT '2.50','35.10','2.50','35.10','0','0',77371
1 rows affected

select A.id,percentage,amount,types from
(
select id,[percentage],row_number() over(order by id) r from [tbl]
		unpivot ([percentage] for N in(CGSTPer,SGSTPer,IGSTPer)) as f1
)A inner join
(
select id,[amount],row_number() over(order by id) r from [tbl]
		unpivot ([amount] for N in(CGSTAmt,SGSTAmt,IGSTAmt)) as f2
)B on A.id=B.id and A.r=B.r
inner join
(
SELECT id,types,row_number() over(order by id) r FROM tbl cross apply (VALUES
  ('cgst'),('sgst'),('igst')
) AS y(types)
)C on A.id=C.id and A.r=C.r
		


id
percentage
amount
types


77371
2.50
35.10
cgst

77371
2.50
35.10
sgst

77371
0.00
0.00
igst


SELECT id,x,row_number() over(order by id) r FROM tbl cross apply (VALUES
  ('cgst'),('sgst'),('igst')
) AS y(x)


id
x
r


77371
cgst
1

77371
sgst
2

77371
igst
3