On 25th of May, ECHA published five documents related to nanomaterials. These documents, 4 which are guidance documents and one which is a recommendation how to prepare REACH registration dossiers containing nanoforms. All these documents are valuable for the 2018 registration deadline as well as for already registered substances. 

These are the documents:
This advises registrants on how to justify the use of hazard data between nanoforms (and the non-nanoforms) and within groups of nanoforms of the same substance.
This document gives recommendations for distinguishing between different nanoforms of a substance, and how to report information on nanoforms consistently in the dossiers. This document was originally intended to be a guidance document, but as a consequence of the Board of Appeal decision in Case A-011-2014, ECHA is publishing this as an advisory best practice document.
The following three existing guidance on nanomaterials, which are the appendices for nanomaterials to Chapter R.7a, R.7b and R.7c of the Guidance on IR&CSA (Endpoint specific guidance) have been updated). These three documents provide nano-specific advice for registrants to meet the information requirements set out in Annexes VI-XI to the REACH Regulation.
Appendix to Chapter R.7a for nanomaterials - Recommendations for physico-chemical endpoints
Appendix to Chapter R.7b for nanomaterials - Recommendations for ecotoxicological endpoints for nanomaterials (general advice, fate and specific endpoints)
Appendix to Chapter R.7c for nanomaterials - Recommendations for ecotoxicological endpoints for nanomaterials (specific advice and specific endpoints)
More information to be found at ECHA website: https://echa.europa.eu/-/reach-guidance-for-nanomaterials-published