Hi Geetha
I am not sure why you would need Cost Centers for returns. It should be reduction in the sales value reported in COPA. In any case, as per VKOA setup, values will flow to FI. I dont see any issue there, however from CO perspective, you need to decide whether the true account assignment object is Cost Center or PSG.
Please note the GL, you have mapped in VKOA would also have an impact. For eg: if the Cost Element is of category 11/12, then it can post to Cost centers (statistically) only if as per Cost center master data, Actual revenue posting is allowed.
For Cost element category 1, you would not be able to post to PSG.
If there are issues above, it will stop releasing the billing document to Accounts (FI)
Hope I answered your concern
Regards
Mustafa Sakerwala