Which of the following statements regarding IRAs is false?

• Taxpayers who participate in an employer-sponsored retirement plan may be allowed to make deductible contributions to a traditional IRA.

• A taxpayer may contribute to a traditional IRA in 2018 but deduct the contribution on her 2017 tax return.

• The ability to make deductible contributions to a traditional IRA and nondeductible contributions to a Roth IRA may be subject to phase-out based on modified AGI.

• Taxpayers who have made nondeductible contributions to a traditional IRA are taxed on the full proceeds when they receive distributions from the IRA.