Roth IRA questions

I thought this forum had an off-topic "money" sub-forum... I guess not.



Anyways, I want to contribute to a Roth IRA, however, my annual income is near the "phase out" limits. Are the phase out limits based on gross income, or net income after deductions?

I already have a 457(b) plan, however, I am not contributing the maximum amount at this time. Would lowering my taxable income by contributing more to my 457(b) plan keep me eligible for a Roth IRA until my income surpasses the eligibility for a Roth IRA?



Thanks for any insight!