This is apparently a 403(b) with a special $3,000 catch-up. I don't see that TurboTax's Smart Check erroneously flags this as an error in the CD/download version of TurboTax, but if in the final check before e-filing TurboTax erroneously says that your total of $29,000 of elective deferrals to the 403(b) include an excess contribution because they exceed the $19,500 regular limit plus the age-50 $6,000 catch-up and prevents you from e-filing, you'll have to print and mail your tax return.
Note that if you contribute to any other 403(b), 401(k) or federal TSP plans, your total elective deferrals to all of these types of plans is not permitted to exceed $29,000 (including your $3,000 special catch-up contribution to the 403(b)).
