The term basis is sometimes used to refer to the amount of contributed funds in a Roth IRA. Roth contributions are not tax deductible, so you've already paid taxes on the money. For this reason, you can look at your Roth contributions as your IRA basis because contributed funds are not taxed when withdrawn.RA Basis. You only have an IRA basis when you make nondeductible contributions to a traditional IRA. You can usually deduct your IRA contributions up to the $5,000 annual limit, or $6,000 when you turn 50.