D.C. Mun. Regs. tit. 8, r. 8-A1108
An employee who receives a temporary assignment to a position to perform the duties and responsibilities of a higher grade may be compensated at that grade whenever possible.
Temporary promotion under the terms of this section shall not exceed one (1) year.
If it is projected that the temporary need to fill a position will exceed sixty (60) days, the position shall be filled through normal competitive selection procedures.
Upon termination of a temporary assignment and return to the previous position, the employee's salary shall be fixed in the previous grade at the step rate to which the employee would have progressed by means of a within-grade increase if the employee had not been assigned to the higher grade.
If the employee received any additional increase based on merit or exemplary performance while assigned to the higher grade position, the employee's salary upon return to the previous position shall be fixed at the step rate immediately above the rate determined in accordance with § 1108.4.
D.C. Mun. Regs. tit. 8, r. 8-A1108