Constitutional Amendment Bill can originate in either House.
Each House has to pass the Bill with two thirds majority of the total membership of that House.
If 2nd House passes the Bill with amendments it is referred back to the House in which it originated and if that House agrees to those amendments with two thirds majority it is sent to the President for assent. If the 2nd House does not agree to the Bill or the amendments the matter ends there and then.
Constitutional amendment Bill which seeks altering the limits of a Province shall also be passed by the Provincial Assembly of that Province by the votes of not less than two thirds of its total membership.