Understanding your IRA basis can help clarify how much of your retirement savings is taxable when withdrawn. The term “IRA basis” refers to the portion of an IRA made up of after-tax contributions, which are not taxed again upon distribution. This concept applies most commonly to traditional IRAs, where nondeductible contributions must be tracked using IRS Form 8606. Without proper tracking, the IRS may treat the entire distribution as taxable.
A financial advisor can help you create a withdrawal strategy to minimize taxes in retirement.
What Is IRA Basis?
IRA basis represents the portion of your traditional IRA that comes from nondeductible contributions—money you’ve already paid taxes on before adding it to your account. Contributions become nondeductible when your income exceeds IRS limits for taking a deduction, and you or your spouse are covered by a workplace retirement plan. In that case, you can still contribute to a traditional IRA, but you won’t receive a tax deduction.
Unlike deductible contributions, which reduce your taxable income when made, nondeductible contributions provide no immediate tax benefit. However, they do create a basis that reduces your tax burden later. When you take distributions, only the earnings and deductible contributions are taxed. The basis is excluded from taxable income, but it must be documented with IRS Form 8606 each year you make a nondeductible contribution or take a distribution.
To illustrate the total basis of an account, let’s say you have an IRA worth $100,000, with a total basis of $20,000. In this example, the $20,000 represents contributions on which you’ve already paid taxes. Therefore, upon withdrawal, you’ll only owe taxes on the remaining $80,000.
If you have multiple IRAs, the IRS treats them as one combined account when calculating how much of a withdrawal is taxable, using a pro-rata formula. This means your IRA basis doesn’t apply only to one specific account—it affects all traditional IRAs you own, regardless of which one you withdraw from.
Why the Total Basis in IRAs Is Important

Understanding your IRA basis is useful for various financial and tax-related reasons. Here are four common ones to keep in mind:
- Tax reporting and avoidance of double taxation: Since traditional IRA distributions typically consist of both deductible and nondeductible contributions, knowing the basis helps avoid double taxation. It allows you to calculate the portion of distributions that represents the return of previously taxed contributions, which is nontaxable.
- Determining taxable amounts in conversions: If you convert a traditional IRA to a Roth IRA, the portion of the conversion that is subject to income tax is calculated based on the ratio of the nondeductible contributions (basis) to the total IRA balance. A higher basis means a smaller taxable portion upon conversion, reducing the immediate tax impact.
- Estate planning and inheritance: Knowing the basis in your IRAs is essential for estate planning purposes. Beneficiaries inheriting IRAs need to be aware of the basis to correctly determine the tax implications of distributions they receive. Understanding the basis can help beneficiaries make informed decisions regarding the timing and structure of withdrawals to minimize tax liabilities.
- IRS compliance and documentation: Accurate recordkeeping of the basis in IRAs is necessary for IRS compliance. Maintaining records of nondeductible contributions helps in substantiating the basis claimed when reporting distributions, conversions, or other IRA-related transactions. Proper documentation ensures compliance with tax regulations and reduces the risk of facing penalties or disputes with tax authorities.
Traditional IRA vs. Roth IRA Basis
The basis of a traditional IRA is the sum of all nondeductible contributions you’ve made. It’s critical to track these contributions to avoid paying taxes again upon withdrawal — especially relevant if you’ve made both deductible and nondeductible contributions to your traditional IRA over the years.
The basis of a Roth IRA is the total amount of contributions made, as Roth contributions are always made after tax. All contributions and qualified distributions, including qualified earnings, are free from income tax.
How to Calculate Your Basis
Calculating your basis in a traditional IRA begins by identifying all nondeductible contributions made. Add these contributions for each year to get your total basis. Consistent tracking of these contributions annually ensures accurate calculation. For example, if you make nondeductible contributions of $5,000 each year for 10 years, your total IRA basis equals $50,000 (10 years x $5,000/year).
Then you must also account for any distributions taken. For example, if you took any money out of your IRA, you’d have to reduce your basis by the nontaxable portion of the distribution.
Tracking Your Basis
Regular monitoring of your IRA basis is not simply a “good practice;” it’s a practical move because it can save you from paying unnecessary taxes upon withdrawal and assist in strategic retirement planning. By staying on top of your IRA basis, you can maximize tax benefits, thereby making the most of your retirement savings. Depending on your situation, it could save you thousands of dollars.
Various techniques exist for tracking IRA basis, such as maintaining a spreadsheet, using financial software or relying on your IRA custodian’s tracking. While no one-size-fits-all, each method has its advantages and can be chosen based on personal preferences and comfort. You may also want to work with a financial advisor who can keep track of this for you.
Bottom Line

Understanding and tracking your IRA basis is key to effective retirement planning. This can help you avoid double taxation, curb your tax liability and guide strategic retirement decisions. As an IRA holder, make a habit of tracking your nondeductible contributions annually. Use tools and methods that best serve your purposes. You may want to seek advice from a tax or financial advisor to ensure you’re tracking and managing your IRA basis effectively.
Tips for Retirement Planning
- A financial advisor can help you think through all of your income needs during retirement and help you plan your investments so you can reach your long-term financial goals. Finding a financial advisor doesn’t have to be hard. SmartAsset’s free tool matches you with vetted financial advisors who serve your area, and you can have a free introductory call with your advisor matches to decide which one you feel is right for you. If you’re ready to find an advisor who can help you achieve your financial goals, get started now.
- You may also benefit from using a retirement calculator to estimate whether you’re saving enough for your retirement.
Photo credit: ©iStock.com/Anna Frank, ©iStock.com/kate_sept2004, ©iStock.com/Rawpixel