How can Excel accept very long formula?

I am creating a formula for Social Security System Bracket computing.
In every row of the condition I have finished, I am testing the formula if the condition shows the right calculation for the salary bracket given.
I am just in the middle of the table when the error message showed as I enter the formula telling that the Formula is too long.
How can I avoid this error message since I need to create a long formula so that I could come up with the right answer?

Error:
Microsoft Excel
Formula is too long.
OK
