Transitional tax provision preserves pre-existing state tax laws inconsistent with the amended Constitution until legislative repeal or expiry. The transitional provision preserves existing state laws taxing goods or services that are inconsistent with the Constitution as amended, permitting those laws to remain in force until amended or repealed by a competent legislature or authority or until the expiration of one year from commencement, whichever is earlier, and contemplates a power to remove implementation difficulties.