Dear Sir,
In Form 12A for the month of September, you should show the number of employees as of the last month, which is the number of employees as of August. Then, in the column of the number of employees left, you should show the number of employees who left. After that, you can calculate the total number of employees in September.
In Form 10 for September, you should include the employee's name, father's name, and date of resignation as of the date he resigned in August. Additionally, provide the reason for leaving.
I hope this clarifies the information for you.
Sindhu