The ARM-version of Office 2013 Home and Student will be bundled with Windows RT devices. Even though Microsoft has not officially confirmed it, word on the streets is that the ARM version of Office 2013 will not have macros, third-party add-ins, or VBA support. A “small number” of additional features will not be available on the ARM-version of Office 2013 according to sources with The Verge.
The reason behind this decision is so that the speed of the tablet will be optimized. The full version of Office 2013 Home and Student RT will not ship with Windows RT tablets this October. They will have a “preview version” of the software and users will have to upgrade after it expires to keep using Office.