Will my annuity readjust if I return to work part time?

If you return to federal service and your pay is offset by the allocable amount of annuity, you must work a minimum of one year (or equivalent to one year if working part time) to collect a supplemental annuity. This means you keep your current pension and they calculate an additional amount for the time worked beyond the original calculation. A reemployed annuitant who completes at least 5 years of actual continuous full-time service and/or part-time service that is equivalent to at least 5 years full-time service, may elect to have their annuity redetermined under the law in effect at the time of separation from reemployment, in lieu of a supplemental annuity. The manual with detailed information on this topic can be found at the following link:
https://www.opm.gov/retirement-services/publications-forms/csrsfers-handbook/c100.pdf