Even though tax filing season is well under way, there's still time to make a regular IRA contribution for 2018. You have until your tax return due date (not including extensions) to contribute up to $5,500 for 2018 ($6,500 if you were age 50 or older on December 31, 2018). For most taxpayers, the contribution deadline for 2018 is April 15, 2019 (April 17 for taxpayers who live in Maine or Massachusetts).
You can contribute to a traditional IRA, a Roth IRA, or both, as long as your total contributions don't exceed the annual limit (or, if less, 100% of your earned income). You may also be able to contribute to an IRA for your spouse for 2018, even if your spouse didn't have any 2018 income.
You can contribute to a traditional IRA for 2018 if you had taxable compensation and you were not age 70½ by December 31, 2018. However, if you or your spouse was covered by an employer-sponsored retirement plan in 2018, then your ability to deduct your contributions may be limited or eliminated, depending on your filing status and modified adjusted gross income (MAGI). (See table below.) Even if you can't make a deductible contribution to a traditional IRA, you can always make a nondeductible (after-tax) contribution, regardless of your income level. However, if you're eligible to contribute to a Roth IRA, in most cases you'll be better off making nondeductible contributions to a Roth, rather than making them to a traditional IRA.