If you lost the serial code, you cannot purchase the upgrade version.

Serial codes can be found in order confirmation e-mails received when purchasing downloads at the VOCALOID SHOP.

If you have a packaged version of VOCALOID4 or an earlier editor, a sticker with the serial number written on it will be affixed to the bottom of the DVD tray in the DVD case.
The location of the serial number for packaged products from VOCALOID5 onwards differs depending on the sales company, so please contact the company that sold you the product for this information.
Please note that we cannot reissue the serial number of a packaged product if you lose it.

By providing the customer information from the time of purchase, we may be able to locate your purchase history. Please contact support for help.