Please elaborate on what needs to be corrected. Does the Form CSA-1099-R (or perhaps several Forms CSA-1099-R if multiple years are involved) issued by OPM not reflect the total of the distributions that you received? If the total reported by OPM on Forms CSA-1099-R does not reflect the correct total, you would need to contact OPM to obtain a corrected form.
When your OPM annuity starts, OPM will have you on interim status and pay an estimated benefit until they get everything processed to determine your actual monthly benefit. Once they have everything worked out they adjust your monthly benefit temporarily to make up for any difference in the payments made while you were on interim status. In the end the Forms CSA-1099-R report the total that was actually paid and that's what you report on your tax return.
