Yes, generally you can make post-tax contributions if all the IRA requirements are met. The total contribution limits are the same. Withdrawals of after-tax contributions to a traditional IRA should not be taxed. However, the only way to make sure this does not happen is to file IRS Form 8606.
Form 8606 for nondeductible contributions
Any money you contribute to a traditional IRA that you do not deduct on your tax return is a “nondeductible contribution.” You still must report these contributions on your return, and you use Form 8606 to do so.
Reporting them saves you money down the road. That’s because no individual’s money is supposed to be subject to federal income tax twice. Form 8606 gets it “on the record” that a portion of the money in your IRA has already been taxed. Later on, when you take distributions, a portion of the money you get back will not be subject to income tax.
Your IRA basis is the total of all your nondeductible IRA contributions (and for all of your traditional IRA accounts, if you have more than one). Contributions do not include rollovers.
TurboTax will guide you... go to Retirement and Investments and continue through the IRA questions until you reach Any Nondeductible Contributions to Your IRA. Answer the prompts and you should have no problem.
