In 1962, UN Resolution 1721B (XVI) required member States of the UN to register objects launched into space. This was a move to reduce tensions and alleviate the fear that the US or the USSR would place weapons in orbit. The resolution was complemented in 1976 when the UN drew up the Convention on Registration of Objects Launched into Outer Space.
Registration documents submitted to the United Nations under the provisions of UN Resolution 1721B (XVI) and article IV of the 1976 Convention on Registration of Objects Launched into Outer Space are published as two series of United Nations documents (UNO 1962, UNO 1977), which are not widely available and in which the information is scattered and hard to find. In the 1990s I (McDowell 1994, with revisions through 2011, http://planet4589.org/space/un/un.html) compiled an edited version of the information in the Registration documents which corrects the above mentioned errors and arranges the information in a systematic way, carefully distinguishing between information included in the registrations and information gained from other sources. Since then, the UN Office of Outer Space Affairs has generated a public database which addresses a similar need ( http://www.oosa.unvienna.org/oosa/en/SORegister/index.html) However, I am continuing my own compilation of the UN data as an independent assessment.
Since 1962, most space payloads have been duly registered with the UN. (The USSR retrospectively registered its pre-1962 payloads, while the US did not.) However, a number have not been registered, in violation of Resolution 1721B. Here (Table 1, linked at bottom) I summarize the situation for launches for the period from the beginning of 1980 to the end of 2013 using the data from my edited version of the Registry, which covers documents published up to early 2015 at oosa.un.org.
Satellites launched in 2014-15 are tabulated separately in Table 1; since the diplomatic world has apparently not yet entered the age of instant communication and still grinds slowly, we can't consider the 2014 satellites to be delinquent yet.
But which satellites should be registered and who should register them? Follow the link for a discussion of the complications involved.
In Table 2 I list all the satellites launched since 1962 which have not been registered with the UN, together with the name of the UN member state which I believe should now register them. In most cases the failure to register was due to adminstrative oversight, or confusion as to which state should be the registrant, and it is to be hoped that the states in question will retrospectively register the satellites in Table 2. The states with the most unregistered satellites launched prior to 2013 Dec 31 are the USA, the People's Republic of China, Israel and Saudi Arabia. There are also 22 unregistered satellites from the former USSR, but half of these are from a single period in Jul-Sep 1970 which likely corresponds to a registration document lost in transmission somehow.
Satellites marked 'P' are uncontroversially payloads; other flags such as e.g. 'PXAU' indicate special cases which might be argued about, but which in my best judgement should have been registered.
I welcome comments and criticisms; please contact me at firstname.lastname@example.org