If it was me I would submit both the a copy of the declaration and the notice by email to RTB at the same time as you give to your tenants. Better they have all the information so the tenant cannot say they did not receive the copy of the declaration which would make the notice invalid.
This is from RTB:
'For all Notices of Termination to be deemed valid, they
must be copied to the RTB at the
same time as it is served on the tenant. Failure to do so means that the Notice of Termination is invalid. Landlords are asked to attach the
Notice of Termination to a completed Notice of Termination return form to assist the RTB in linking the Notice to the relevant tenancy.
It can be emailed to
[email protected] or posted to the Residential Tenancies Board, PO Box 47 Clonakilty, Co. Cork.
If posting, the RTB recommends using certified post to ensure landlords have proof of the date the RTB was sent the copy of the Notice of Termination. These documents must be sent to the Residential Tenancies Board on the
same day as the notice is served on the tenant. Landlords should retain copies and proof of postage for their records.