There is no periodicity provided for maintaining Form D as prescribed under the ERA. However, the same is to be maintained/updated whenever there is a change in the establishment with respect to the entries to be made therein, i.e., the number of employees, their salary, etc.
Inclusion of All Cadres of Employees
The Form D is required to include all cadres of employees irrespective of whether they are ordinary workers or working in a supervisory managerial capacity. However, in the column "category of workers," you can distinguish between different employees/workers as per their job profile. For example, if there are two workers, and both are skilled but one is a machineman and the other is a lathe man, you can distinguish between them and enumerate their respective work/duties in column no. 2, i.e., a brief description of work.
Regards