time of removal supply of goods

removal of goods is the time of invoice preparation
and payment due/made is in case of service

Goods :

As per Section 31 of CGsT Act :

A registered person supplying taxable goods shall, before or at the time of,—
(a) removal of goods for supply to the recipient, where the supply involves
movement of goods; or
(b) delivery of goods or making available thereof to the recipient, in any other
case,

In case of Service
As per Section 13 of CGST Act :
The time of supply of services is earlier of following

1.Date of ssue of Invoice
2. if invoice is not issued within prescribe time or date of receipt of payment whichever is earlier
3. Recepient show recepit of services in his books of Account (when 1 & 2 not applicable)