There are a lot of sellers who sell on multiple eBay sites and/or have multiple eBay User IDs. Now, imagine a case where you have say one quantity of an item, but you wish to list it on multiple eBay sites, say, US, UK as well as Australia. In addition, on each site, you actually want one fixed price listing and another as an auction. So, across all three sites in two different formats will result in a total of six listings. BUT you only have one quantity. So, when any listing is SOLD, you MUST ensure that you END all other five remaining listings IMMEDIATELY, otherwise, you stand the risk of over selling.
Wonder Lister Solution:
In Wonder Lister, you can set a preference (a simple checkbox!) that essentially says that when a listing with a given SKU ends, automatically END all other Active Listings with the same SKU. And that’s pretty much it.
Based on the above, as you can see, the ONLY requirement is that all listings share a common SKU which they should in the first place as they all represent the same physical item.