Certain items that are taken out pretaxed are available to be changed during open enrollment. Open Enrollment for most companies occurs in conjunction with the fiscal year of the company, governments too.
Many times companies will send out a notice that if you do not respond by a certain time then changes will be made on your behalf. An individual simply by not responding, has made a choice for change.
Any time that a change occurs with an individual's pay, I always advise to first check with payroll or human resources first. Many times people find out that a simple mistake has happened and the payroll department can make any corrections needed.
My advice is to check with payroll and find out if your withholding is correct.They will be able to advise on all items and if you missed a chance to update your withholding then they can take care of that for you.
I did find that in Iowa,
Deductions at a rate determined by the Iowa State Legislature are made from each employee's check. So it appears that a change to the annuity amount was determined.
I sincerely XXXXX XXXXX this information is helpful ,
If the legislature changed the rate , which it appears they have based on the change in your withholding, then yes they can do this at their discretion.
Since this si a state regulated annuity the legislature can make the changes without consent. Perhaps you can register your concerns with your representative.
Changesto other things, like insurance or if you have child care taken out pretaxed and then reimbursed to you yes, you must authorize the amounts. The annuity is paid into a state program and added to city and state monies for investment to have a larger amount and in theory make more money for the contributors.
Ask your payroll department if your city employees are paying into the state annuity for employees.