The TaxAct program does not provide Alerts regarding the limits on deferred income as there are many situations where the limits may vary. This is outlined in detail in IRS Publication 525 Taxable and Nontaxable Income. Your employer or plan administrator should apply the proper annual limit when figuring your plan contributions; however, you are ultimately responsible for ensuring they are correct.
Per IRS Publication 525 Taxable and Nontaxable Income, page 9:
Your employer's contributions to a qualified retirement plan for you aren’t included in income at the time contributed. (Your employer can tell you whether your retirement plan is qualified.) However, the cost of life insurance coverage included in the plan may have to be included.
If your employer pays into a nonqualified plan for you, you generally must include the contributions in your income as wages for the tax year in which the contributions are made. However, if your interest in the plan isn't transferable or is subject to a substantial risk of forfeiture (you have a good chance of losing it) at the time of the contribution, you don't have to include the value of your interest in your income until it is transferable or is no longer subject to a substantial risk of forfeiture.
If you’re covered by certain kinds of retirement plans, you can choose to have part of your compensation contributed by your employer to a retirement fund, rather than have it paid to you. The amount you set aside (called an elective deferral) is treated as an employer contribution to a qualified plan. An elective deferral, other than a designated Roth contribution (discussed later), isn't included in wages subject to income tax at the time contributed. However, it’s included in wages subject to social security and Medicare taxes.
Elective deferrals include elective contributions to the following retirement plans.
Overall limit on deferrals. For 2019, you shouldn't have deferred more than a total of $19,000 of contributions to the plans listed in (1) through (3), earlier, unless you are 50 or older. The specific plan limits for the plans listed in (4) through (7), earlier, are discussed later. Amounts deferred under specific plan limits are part of the overall limit on deferrals.
Your employer or plan administrator should apply the proper annual limit when figuring your plan contributions. However, you’re responsible for monitoring the total you defer to ensure that the deferrals aren't more than the overall limit.
[The publication continues with the limitations based on specific circumstances.]