When I built the database that runs this website I created a list of 17 status codes that I hoped would cover every possible 'state' of a given rolling stock number. These codes are listed below, along with some information about what they apply to.
Every number in the database will eventually have a status code, to enable filtering (such as to show only 'current' numbers). Note that there is a bit of overlap between some categories, especially in terms of stock that is preserved but which is/was registered to run on the main-line.
||Notes about usage
||Extant, Registered, Active
||This status applies to all rolling stock in routine use on the national rail network. Stock of the passenger and freight TOCs is covered, along with infrastructure companies, rolling stock lessors and hirers, and preserved stock that is not confined to heritage lines.
||Extant, Registered, Overseas (Temporary)
||Primarily intended for use to indicate locomotives that are working abroad but which sometimes return to the UK for maintenance or other reasons (e.g. ECR class 66 locos). Can also be used for foreign-registered wagons that used to work to the UK but have not done so for a year or more.
||Non-extant, Un-registered, Cancelled
||This code indicates a number which was planned to be applied to new/converted/renumbered stock but which in the event did not happen. Its use on this website is unlikely, since cancelled numbers are not normally added to the database.
||Non-extant, Un-registered, Disbanded
||This category is only for multiple unit set formations that no longer exist. If the whole set was renumbered or scrapped (without a formation change), the relevant status codes should be used instead. However, if 2 coaches from a unit were scrapped while the other 2 were preserved, the set number should be shown as status 'Disbanded'.
||Extant, Un-registered, Grounded
||Intended primarily for grounded bodies, such as vans in use as store sheds on farms, or tank wagons used for static oil storage. Can also be used for stock that is complete but off-tracked, or on isolated track, though these should be in category 'Preserved' or 'Industrial/Other' if more appropriate.
||Extant, Un-registered, Internal User
||This category originally applied to stock that was renumbered in the Internal User series, and either immobilised or used only within confined areas (such as a yard or depot). For more recent examples, stock that is in use but not TOPS registered (such as the class 09 shunter with London Overground at Willesden) can be in this category, or in 'Industrial/Other'.
||Non-extant, Registered, Lost
||This status indicates an item of stock that is still showing as current on TOPS but which has actually already been scrapped (or renumbered, exported, etc).
||Extant, Un-registered, Metro/Other
||Stock only used on tube/metro/tram systems such as the London Underground.
||Extant, Un-registered, Industrial/Other
||This category can be used for any non-preserved stock that is in some form of use but not registered for use on the national network. Examples would include locos and wagons at industrial locations and former coaches used for emergency services training. TOPS-registered stock should be in this category if it does not actually use network tracks on a regular basis.
||Non-extant, Registered, On Order
||Numbers are often added to TOPS before the stock is actually delivered. This status code can be used for these, being updated to 'Active' once the items are delivered.
||Extant, Un-registered, Preserved
||Stock that is confined to heritage lines (or museums) and is not mainline-registered. Should also be used for stock that is/was TOPS registered but which is not routinely used on the mainline. Note that this category can cover everything from fully-restored stock to 'wrecks' awaiting attention. The actual condition of each item can be shown by notes.
||Non-extant, Un-registered, Re-numbered
||Indicates a number that is no longer current because the item of stock that it applied to has subsequently been given a different number.
||Extant, Registered, Stored
||Used for stock that would be in category 'Active' but which is known to have been out of use for a month or more.
||Extant, Un-registered, Withdrawn
||This category is for any stock that is in long term storage pending disposal, and which is no longer registered on TOPS. Examples would include the collection of wagons dumped for many years at Ripple Lane (though these have now gone).
||Extant, Un-registered, Exported (Permanent)
||Primarily intended for locos that are sent to work abroad with little prospect of returning to the UK (e.g. class 66s in Poland and class 87s in Bulgaria). Can also be used for foreign-registered wagons that used to work to the UK but can no longer do so (such as chemical tank wagons).
||Non-extant, Un-registered, Unknown, Presumed Scrap
||This is the default category for stock which is believed to have been scrapped but where the details have not (yet) been confirmed. Status can also be used for older foreign-registered wagons that no longer visit the UK and for which current information is not available.
||Non-extant, Un-registered, Scrapped
||Indicates an item of rolling stock that is known to have been scrapped (ideally with the disposal date also recorded). If there is any doubt, use category 'Presumed Scrapped'.