Per IRS Publication 590-A Contributions to Individual Retirement Arrangements (IRAs), page 38:

How Much Can Be Contributed?

The contribution limit for Roth IRAs generally depends on whether contributions are made only to Roth IRAs or to both traditional IRAs and Roth IRAs.

Roth IRAs only. If contributions are made only to Roth IRAs, your contribution limit is generally the lesser of:

• $6,000 ($7,000 if you are age 50 or older), or
• Your taxable compensation.

However, if your modified AGI is above a certain amount, your contribution limit may be reduced, as explained later under Contribution limit reduced.

Roth IRAs and traditional IRAs. If contributions are made to both Roth IRAs and traditional IRAs established for your benefit, your contribution limit for Roth IRAs is generally the same as your limit would be if contributions were made only to Roth IRAs, but then reduced by all contributions for the year to all IRAs other than Roth IRAs. Employer contributions under a SEP or SIMPLE IRA plan don’t affect this limit.

This means that your contribution limit is the lesser of:

• $6,000 ($7,000 if you are age 50 or older) minus all contributions (other than employer contributions under a SEP or SIMPLE IRA plan) for the year to all IRAs other than Roth IRAs, or
• Your taxable compensation minus all contributions (other than employer contributions under a SEP or SIMPLE IRA plan) for the year to all IRAs other than Roth IRAs.

However, if your modified AGI is above a certain amount, your contribution limit may be reduced, as explained later under Contribution limit reduced.

Simplified employee pensions (SEPs) and savings incentive match plans for employees (SIMPLE plans) are discussed in Pub. 560.

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