Tds

TDS is to be deducted

  -at the time of crediting the bill to the supplier or

  -at the time of payment of the bill

whichever is earlier

If you book the bill or make payment of the bill in April 2016

the TDS should be deducted in April 2016 and paid int May 2016

Hope this helps you

Agree with Chandra Ji but i want to add some point

In few cases TDS has to be deducted while making payment to the payee (payment basis);

1. Salary
2. Dividends
3. Winning from lottery or crossword puzzle
4. Winning from horse-race
5. Payment in respect of deposits under NSC
6. Payments in respect of repurchase of units by mutual fund or unit trust of India
7. Payment of compensation on acquisition of certain immovable property

Except these 7 cases, in all other cases we need to deduct it at the time of credit or payment which ever is earlier.