This is because when you initially enter the contribution, it lets you take a deduction for it which reduces your tax burden since but when you answer all the other questions including adding all you income and whether you and your spouse were covered by a Retirement Plan at Work, it makes a determination that your MAGI is too high and does not let you take a deduction which increases the tax burden.
Your traditional IRA contributions may be tax-deductible. The deduction may be limited if you or your spouse is covered by a retirement plan at work and your income exceeds certain levels.
