Any contributions to benefit plans made on a pre-tax basis are not PERA-includable salary. That means that you won't pay PERA a percentage of your costs for these deductions. That also means that PERA won't count the money you spend on benefit plans towards your Highest Average Salary. If you're nearing retirement, this might affect you. 

Paying for any of these benefits on a post-tax basis makes them PERA-includable. PERA will collect a percentage of the money you contribute to plans, but they also will count that towards your Highest Average Salary. Contributions to DPS voluntary retirement plans – such as 403(b), 457, or 401(k) Roth – are not PERA includable. 

Definitions:
Pre-tax: this means that your benefit deductions come out of your salary before your income tax is calculated and deducted. This ultimately saves you some dollars on income taxes, but also lowers your Highest Average Salary with PERA. 
Post-tax: this means that your benefit deductions come out of your salary after your income tax is calculated. This means that you pay more in taxes, but PERA counts your full salary towards your Highest Average Salary. 
Highest Average Salary: this is the amount that PERA uses when they calculate your retirement payments. Visit CO PERA to learn more about your PERA benefits and how your Highest Average Salary is calculated. 

For more information, please contact PERA at 303-832-9550 or 1-800-759-7372 Monday–Thursday, 7:00 a.m. to 5:30 p.m.; Friday, 7:00 a.m. to 4:30 p.m. (Mountain time).

Example only. Actual amounts will vary from person to person.