Japanese customs regulations, including change of tariff rate, Generalized System of Preferences (GSP) scheme update, introducing customs facilitation system etc, are in most cases implemented annually in April.
I reviewed FY2012 customs regulation proposed changes, which are awaiting the review by Diet at this point of time, and find this year's most useful topic for trader would be "(hard copy) invoice is no longer required in customs declaration".
Currently, Customs Law Article 68 stipulate like as follows, "invoice (called "Shiiresho" in Japanese, imply hard copy) should be submitted in export and import customs declaration unless customs advise otherwise."
Off course, Japan customs have state of the art e-customs declaration system, called as NACCS.
But still, exporter/importer have to submit invoice (hard copy) to customs authority for all declarations based on the Customs Law Article 68.
By amending Article 68, invoice submission is basically no longer required unless customs request, e.g. in more precise review or cargo inspecting case. Trader's obligation is to keep the invoice either electrically or in documents, and if customs request to submit, just do so. Therefore, in normal operation, traders will not be required to submit hard copy invoice in each time of customs declaration.
As for implementation timeline, it is expected from July 2012. As NACCS system's program change is necessary, due to its system work, it cannot be started from April 2012.