If one cultivates the habit of going through the "Statement of Objects and Reasons" attached to any Act of the Parliament or State Legislature whether it be an original Act or an Amending Act, such a question would not arise at all.
When a Bill is passed by the Parliament or State Legislature on a particular subject-matter for the first time, it is called the original Act with its short title comprising the year of its enactment. The short title " The Payment of Wages Act, 1936 " denotes it is the Act on the subject-matter of Payment of Wages originally enacted in the year 1936.
When certain provisions of the existing original Act are just modified, deleted or newly added during any year thereafter depending on the need of the subsequent times without repealing the entire Act, such process is called " amendment " and the particular subsequent Act carrying out the amendments to the original Act is called with the same short title comprising the term " Amendment" in brackets and the year of its passing.
For example, " The Payment of Wages (AMENDMENT) Act, 2017" means it is the Act amending certain provisions of the existing " Payment of Wages Act,1936" in the year 2017. If we read the " Statement of Objects and Reasons " attached to the Amendment Act, we would understand the circumstances and reasons necessitating the amendments to the existing Original Act. The existing PW Act,1936 would be in force with the amended provisions with effect from the date notified under the Amending Act. It is not a new Act replacing the entire original Act and as such no necessity for any confusion such as old and new Acts. You can carry out the amendments with the effective dates in your personal copy of the existing Act.
27th March 2017 From India, Salem