From HEXONET Wiki
The RenewDomain command is used to renew domains explicitly for a specified time period at the registry . When renewing a domain please enter the domain, the period for renewal (e.g. period = 1) and the current expiration year (e.g. 2007). Please notice that you can not explicitly renew domains under all TLDs. For further information please see the corresponding TLD info page.
(required) command = RenewDomain domain = (DOMAIN) (optional) period = (INT) expiration = (INT)
(required) code = (CODE) description = (DESCRIPTION) property[registrationexpirationdate] = (DATE) property[status][n] = (DOMAINSTATUS)
Please have a look at HEXONET Renewal System to understand how the system internal renewal works.