5 CFR §430.207

1. (a)Minimum period. An appraisal program shall establish a minimum period of performance that must be completed before a performance rating may be prepared.
2. (b)Ongoing appraisal. An appraisal program shall include methods for appraising each critical and non-critical element during the appraisal period. Performance on each critical and non-critical element shall be appraised against its performance standard(s). Ongoing appraisal methods shall include, but not be limited to, conducting one or more progress reviews during each appraisal period.
3. (c)Marginal performance. Appraisal programs should provide assistance whenever performance is determined to be below “Fully Successful” or equivalent but above “Unacceptable.”
4. (d)Unacceptable performance. An appraisal program shall provide for—
   1. (1)Assisting employees in improving unacceptable performance at any time during the appraisal period that performance is determined to be unacceptable in one or more critical elements; and
   2. (2)Taking action based on unacceptable performance.