GST Rate on work Contract

work contract service for what?.....

In term of Section 14 CGST Act :

IF Supply is made Before Change of Rate :

Date of Issue of Invoice is After change in Rate , Receipt of payment after change of rate or before change of Rate , then the New rate of GST will be Applicable.

As per section 14 of CGST Act,2017
If supply is before such changes and invoices is also received before such change then then rate will be of invoice date but in other if receipt is received before such change then rate will be on the receipt day but if both are after such change then invoice or receipt whichever is earlier...

No Invoice has been raised and also receipt has not been received only agreement has been done @ 18% then what to do now to at the time of issuing invoice to charge 18% (agreement base) or charge 12% (current rate base)

have to charge 12% GST