Designated Class 85 under TOPS the forty members of this Class, initially numbered in the range E3056 to E3095, were renumbered 85001 to 85040 in sequence.

As built this Class designated as Class 86 was delivered numbered in the E31XX series from E3101 to E3200. Although numbered consecutively the Class was delivered into service in a fairly random unordered manner which turned out to be a precursor of things to come when renumbering into the TOPS number range was implemented.
By the time renumbering the fleet to 86XXX began several members of the Class had been modified to a higher power output. These were classified as 86/2 and renumbered into the 862XX series from 86201 onwards. The remaining members of the Class still in as built condition were classified as 86/0 and renumbered into the 860XX series from 86001 onwards. Quite why the 86/1 Sub Class was not used at this point is not entirely clear although the 861XX series was soon utilised for the first three 86/2s subsequently upgraded as test beds for the later build Class 87. These three were renumbered from 86201 86202 and 86203 to 86101 86102 and 86103.
Renumbering into the 86/0 and 86/2 number ranges was undertaken completely at random. For example E3101 the lowest numbered member of the Class in the E31XX number range became 86252 at the end of the 86/2 series whilst E3199 from almost the end of the E31XX series became 86001.

After renumbering into the TOPS number ranges the Class 86s were numbered in the following groups.

86/0: 86001 to 86048
86/1: 86101 to 86103
86/2: 86204 to 86252

The next round of changes came with the last nine from the 86/0 series, 86040 to 86048 inclusive, being upgraded to 86/2 standards and renumbered at random into the number range 86253 to 86261 leaving the Class numbered as follows.

86/0: 86001 to 86039
86/1: 86101 to 86103
86/2: 86204 to 86261

Several programs of upgrades with the 86/0 series locomotives were implemented over time and on upgrading renumbering, initially to the 863XX series then to 864XX, took place to reflect the changes made. Whilst several members from the 86/0 Sub Class were renumbered into the 863XX series others on receiving a higher level of modification were renumbered into the 864XX number range. All those renumbered to 863XX later received the full package of upgrades and in turn themselves were renumbered into the 864XX series. During this round of renumbering the final two digits were retained in that, for example, 86020 became 86320 before becoming 86420 whilst 86006 was renumbered directly to 86406. 86001 to 86010, 86030 to 86039 became 86401 to 86410, 86430 to 86439 directly whilst 86011 to 86029 inclusive became 86311 to 86329 before becoming 86411 to 86429.

86/1: 86101 to 86103
86/2: 86204 to 86261
86/4: 86401 to 86439

The first 86/5 Sub Class was created to accommodate eight 86/2s dedicated to the freight sector subsequently being renumbered from the 86/2 series to the 86/5 series in the number range 86501 to 86508. These eight locomotives were all later returned to 86/2 specification and renumbered back to their former identities.

86205 became 86503 before reverting to 86205
86217 became 86504 before reverting to 86217
86222 became 86502 before reverting to 86222
86233 became 86506 before reverting to 86233
86239 became 86507 before reverting to 86239
86241 became 86508 before reverting to 86241
86246 became 86505 before reverting to 86246
86258 became 86501 before reverting to 86258

86/6, another Sub Class for dedicated freight locomotives, lower speed and ETH capacity isolated, was then created for those from the 864XX series so treated and these were renumbered into the 866XX series, again keeping their last two digits on renumbering. Several Class 86s renumbered into the 866XX number range from the 864XX series have been reclassified back to 86/4s however all but one of these has later been reclassified back to 86/6 and renumbered again into the 866XX series.

86401 86417 86419 86424 86425 86426 86429 and 86430 have remained numbered as such.
86416 became 86616 before reverting to 86416 and stayed numbered as such.

86402 86403 86404 86406 86407 86408 86409 86410 86412 86413 86418 86420 86421 86422 86423 86427 86432 to 86439 have been renumbered to 86602 86603 86604 etc. and have not been renumbered back whilst 86605 86611 86614 86615 86628 and 86631 have spent some time renumbered back to 86405 86411 86414 86415 86428 and 86431 before reverting to their respective 86/6 series numbers.

86/0: 86101 to 86103
86/2: 86204 to 86261
86/4: 86401 86416 86417 86419 86424 86425 86426 86429 and 86430
86/6: 86602 86603 86604 86606 to 86610 86612 86613 86618 86620 to 86623 86627 86632 to 86639

A second 86/5 Sub Class has been created for a re-geared 86/6 and 86608 has been renumbered 86501, the second Class 86 to use this number, whilst the 86/9 Sub Class has been established for two Class 86s converted to mobile self propelled special uses locomotives; 86210 and 86253 being renumbered to 86902 and 86901 respectively.