How to Calculate Tax in SQL?

Transact-SQL
2

One way to do this is as follows.

DECLARE @Income DECIMAL(18,2) = 45000;

SELECT
	TotalTax = SUM( CASE WHEN c > 0 THEN c ELSE 0 END ) 
FROM
	(
		VALUES
			( 0.105 * (CASE WHEN @Income > 14000 THEN 14000 ELSE @income END)  ),
			( 0.175 * (CASE WHEN @Income > 48000 THEN 48000 ELSE @income END - 14000) ),
			( 0.300 * (CASE WHEN @Income > 70000 THEN 70000 ELSE @income END - 48000) ),
			( 0.330 * (@income - 70000 ) )
    ) T(c);