Who is responsible to pay taxes

Generally, the person effecting taxable supplies is liable to pay taxes. However, following are certain exceptions:
(a) Reverse charge: On supply of goods as specified under Notification 04/2017- Central Tax (Rate), dated 28.06.2017 and on supply of services as specified under Notification 13/2017- Central Tax (Rate), dated 28.06.2017 or such other goods or services, as may be notified by the Government on the
recommendations of the Council, the tax shall be paid by the recipient under reverse charge; and
(b) E-Commerce: Categories of services as specified under Notification 17/2017- Central Tax (Rate), dated 28.06.2017 or such other services as may be notified by the Government on the recommendations of the Council the tax shall be paid by the electronic commerce operator if such services are supplied through it.

(ICAI FAQ PUBLICATION 06-09-2017 LEVY AND COLLECTION:  FAQ NO. 16)