Tiered applications are those which have a tree-like menu structure consisting of menus and sub-menus. Most IVRs are of this type. Callers might choose from 4 options at a main menu, say, Accounts, Billing, Technical Support, and All Other Issues (but see Number of Options on a Menu for guidance on breadth versus depth in tiered menu design). Once Billing is chosen, there might be sub-menus with items like “Pay My Bill”, “Enroll in Auto-Pay”, etc. Callers are progressing through an application whose call-flow diagram would look like a tree.

Linear applications are those which are more of a question-and-answer type, and where the caller progresses from one question to another in a linear fashion (even though the question to which they progress may be determined by their answer to the previous question). Technical troubleshooting applications may be linear in nature, or applications along the lines of software product activation, where the caller has a single task which must be broken up because of its complexity (entering a long alphanumeric string, broken up into chunks, turn by turn). Another common example is a bill pay process.

Navigation for these two types of applications can vary. In the menu-driven, tiered application, callers are being asked to select the option which most closely reflects their needs. Global commands such as “help” (“more information”; see Help and Commands) may need to be repeated at points where they help callers, i.e., on a context-sensitive basis. This is the type of application where “go back” is often not recommended, especially for applications in which callers' mental models may not reflect the actual location to which they will go back. (For more information on the Go Back command, see Commands.)

For linear applications, on the other hand, “go back” may be appropriate, as it is typically more straightforward in this context. In addition, the navigational commands in use in a linear application often will not vary that much; for example, after each step, callers may hear “Say 'previous', 'next', or I'm done'.” Given that there be little change in the commands and callers can remember them easily after the first couple of times hearing them, you can taper the commands. So the first time, it might be “To hear that again, say 'previous', for the next step, say 'next', or if you're finished, say 'I'm done”; the next step may be “Say 'previous', 'next', or I'm done', and subsequent times simply “Previous, next, or I'm done?”