If you have created an unsatisfactory EICR and attend at a later date to carry out recommended remedial work your Client will almost certainly ask for a follow up satisfactory report after the work has been carried out.
In this case it is not possible to amend the previous report and change the outcome from unsatisfactory to satisfactory. You should retain the original report for your records and use the copy report facility to create your new satisfactory report as shown in this help article. You can then make the necessary changes including outcome, dates and observations.