Tds payment from a company to professional consultant

We had deployed a consultant for rendering professional services at our customer site for which the payment was to be received after 2 months of raising Invoice.
We had put the same condition to consultant.
Since TDS payment calculation is from the date of deducting the payment, in this case we will deduct the TDS after receiving the payment i.e. after 2 months.
So I hope TDS deposit for consultant has to be done after receiving the payment??
When should be the actuall declaration of TDS? On receiving the payment Or At raising the Invoice?