Tds on catering

It cannot amount to double taxation. VAT is charged on food supply by the vendor. Customer while making payment/credit of catering charges deducts tax at source (on the bill value) and remits the same to govt. The vendor can get credit of such deduction while filing ITR.

Agreed with Poornima

VAT

VAT is a system of indirect taxation. It is the tax paid by the producers, manufactures, retailers or any other dealer who add value to the goods and that is ultimately passed on to the consumer(ultimately paid by public).

TDS

Persons responsible for making payments are required to deduct tax at source at prescribed rates. Instead of receiving tax on your income (Vendor Income) from you (Vendor) at a later date, the govt wants the payers to deduct tax before hand and deposit it with the govt.
The recipient of income receives the net amount (after deducted of tax at source). The recipient will add the gross amount to his income and the amount deducted at source is adjusted against his final tax liability. Basically take credit of the amount already deducted and paid on his behalf.