Bonus year is decided by the accounting year. if you have accounting year from Jan to Dec then Bonus will we made from Jan to Dec and if the accounting year is from April to March then Bonus will be made from April to March.
now coming to your query -
Form C is made for individual bonus details calculation along with many more details as like -
EMPLOYEE NAME
FATHER'S NAME
WHETHER HE HAS COMPLETED 15 YEARS OF AGE AT THE BEGINNING OF THE ACCOUNTING,
NO. OF DAYS WORKED IN THE YEAR,
TOTAL SALARY OR WAGES IN RESPECT OF THE ACCOUNTING YEAR, AMT OF BONUS PAYABLE UNDER SECTION 10 AND 11, AS THE CASE MAY BE
PUJA BONS OR OTHER CUSTOMARY BONS PAID DUR THE ACCOUNTING YEAR
INTERIM BONUS OR BONUS PAID IN ADVANCE
AMOUNT OF INCOME-TAX DEDUCTED
DEDUCTION ON ACCOUNT OF FINANCIAL LOSS, IF ANY CAUSD BY MISCONDUCT OF THE EMPLOYEE
TOTAL SUM DEDUCTED UNDER COLUMNS (9,10,10A,11)
NET PAYABLE (COLUMN 8 MINUS COLUMN 12)
AMT ACTUALLY PAID
DATE ON WHICH PAID
Whereas Form D is the Total Summary of Form C and pertaining the following details -
Total amount payable as bonus under sec 10 or 11 of the payment of bonus act,1965 as the case may be
Settlement, if any , reached under section 18 (1) or 12 (3) of the industrial dispute act,1947 with date
Percentage of bonus declared to be paid.
Total amount of bonus actually paid.
Date on which payment made
Whether bonus has been paid to all the employees, if not,reasons for non-payment
Remarks
So it is mandatory to submit the Form C, Form D along with Form A & B