Clarification on applicability of s tax on retainership

We have engaged a full time consultant on a monthly retainer fee of Rs. 75,000/- pm.

The total consultancy charges per annum works out to Rs. 9,00,000/-.

The consultant is not registered for service tax.

In the bill submitted to us, he has not charged any Service Tax.

What is the liability to the company under this circumstance.

Will the company be liable to pay service tax to the government on obtaining such service.

Please clarify on this matter.

Thanking you in anticipation.