I have worked 47, years. This makes 35, under Social Security. I worked 37, at IRS. I switched to FERS in 1998. I have 21, years substantial earning years. I turned 62, in 2016. My pension is part CSRS part Fers coponents ,19 cars 18 FERS. My estimate is 1335 a month if WEP occurs how much will it be reduced? We were sold it would not be.
If you're drawing a government pension based on your earnings, and if even part of the earnings on which the pension is based were exempt from Social Security taxes then your Social Security retirement benefits will potentially be subject to reduction caused by the Windfall Elimination Provision (WEP). If you have fewer than 30 years of substantial Social Security covered earnings then you won't be fully exempt from a WEP reduction, but the amount of reduction could be reduced if you have between 20 and 30 years of substantial earnings (https://www.ssa.gov/pubs/EN-05-10045.pdf).
There is a WEP guarantee provision that would limit the WEP reduction in your Social Security benefit rate to no more than 50% of the portion of your government pension that's based on your non Social Security covered earnings. So, for example, if your full government pension amount was $1200 and half of that amount was based on your non-covered earnings, then the WEP guarantee would limit your reduction to no more than $300 (i.e. 50% of 50% of $1200).
However, the normal WEP benefit computation formula never reduces a person's benefit rate by more than roughly $480, so the WEP guarantee is only used when the person's government pension amount is relatively low. And, since you apparently have more than 20 substantial years of Social Security covered earnings, the amount of reduction in your monthly rate would definitely be less than $480.
I can't give you a precise amount of how much your WEP reduction will be, but our software (https://maximizemysocialsecurity.com/purchase) is fully programmed to handle WEP calculations so you may want to strongly consider using it to do your Social Security planning.