I am trying to develop a computer program to compute the tax for a given base salary, I believe given the format of the income tax table that I have there should be a formula to calculate the tax for a given base salary. Below is the sample format of income tax table.
Annual Salary Monthly From Ranges To Tax Due
18,000.00 0.00 1,500.00 0.00
18,060.00 1,500.01 1,505.00 0.25
18,120.00 1,505.01 1,510.00 0.50
18,180.00 1,510.01 1,515.00 0.75
18,240.00 1,515.01 1,520.00 1.00
18,300.00 1,520.01 1,525.00 1.25
18,360.00 1,525.01 1,530.00 1.50
As you can see for every range of salary there is an increment of .25 on tax. I have tried to find my own formula but I could not find an accurate one.
Your tax is $0.25$ on every $5.00$ or portion above $1500$. So you can use $\lceil \frac {\text{monthly}-1500} 5 \rceil \cdot 0.25$