ECHA recently provided additional information in a press release of 8 October related to nanomaterials and REACH

From1 January 2020 additional information on nanoforms of substances will need to be provided in REACH dossiers.

The amendments of the REACH Annexes for nanomaterials (nanoforms) apply to all new and existing registrations covering nanoforms. This means that industries should update their existing dossiers with nanoform-specific information by 1 January 2020.

To support this, IUCLID will be updated on 30 October. 

With regard to guidelines ECHA provides the following. 

'ECHA’s new nano-specific guidance helps companies to comply with the changes in Annex VI. In addition, the guidance on read-across between nanoforms or sets of nanoforms is being updated to reflect the changes. Both documents are expected to be ready by the end of 2019. The draft documents are published on the ongoing guidance consultation page.
The 2017 ECHA guidance for human health and the environment is also being updated. The OECD is revising some of their existing test guidelines used under REACH, to ensure that data generated on nanoforms is reliable and meets regulatory standards. An overview of the revised REACH Annexes and the available test methods are available on the EU observatory for nanomaterials (EUON).'
NIA recent news about the guidance document, indicating some new paragraphs in comparison to previous version.