According to pgcet notification

Caste certificate / caste income certificate / income certificate should be obtained in the name of the candidate only.

The candidates belonging to SC, ST and Category –1 of the Other backward classes should also produce a separate Income Certificate to claim Tuition Fee Exemption from concerned department / Government of India scholarship as per the prescribed format.

If you have the income certificate of the date before the date of last date of application form you can use your income certificate.

However,Income certificates are usually valid for one year from the date of issue. You can renew your income certificate online if your income status hasn't changed since the last issuance.