Military intelligence was not referred to legacy inquests by police in Northern Ireland because of an oversight, a presiding coroner said.
The PSNI has held a database containing MoD intelligence since 2007.
The force's Disclosure Unit was "not aware" of this so did not routinely search the MoD database when compiling disclosure of intelligence material for the coroner, a statement from the Coroner's Service said.
Presiding coroner Mrs Justice Siobhan Keegan said: "The Chief Constable, on becoming aware of this issue, directed in December 2017 that PSNI will now also routinely search the MoD military intelligence database which it holds to ensure full disclosure of any material held to the coroner."
As part of pre-inquest proceedings the PSNI did check its own database and also one shared with the MoD; this material was provided to coroners, the presiding coroner added.
She intends to develop a disclosure protocol and will issue a draft for consultation in the coming weeks.
The judge added: "The MoD has of course provided its own disclosure of military intelligence material to coroners and it is to be expected that this material should be the same as that which is on the database in the possession of the PSNI.
"An exercise is already under way in an ongoing inquest to compare the material which PSNI has uncovered by searching the MoD database it holds with the material which the MoD had previously provided by way of disclosure to the coroner and to date no major discrepancies have been found."
The PSNI is conducting searches of the MoD database it holds for live inquests and will provide the material for determination of potential relevance to the coroner's legal representatives for comparison with any MoD material already disclosed.
The PSNI has assured the Coroners Service of its continued co-operation and commitment to work with the coroners in relation to all matters affecting legacy inquests.
The MOD has stated that it has always fully complied with all of its legal and statutory obligations in regard to disclosure of legacy material, including historic intelligence material and that the discovery process involves searching a wide variety of systems and archives.
This includes - and has always included - military intelligence records held in shared intelligence databases operated jointly with partner organisations.
The coroner's statement added: "Inquests which are listed for hearing this calendar year are on track and should be capable of being heard in accordance with planned timescales."