Habitual residence seems easy enough to prove. No harder than packing up your bags, buying a one way ticket here and joining the local library. EU’s 65+ citizens would be mad not to.
Proof to show you have given up accommodation abroad (e.g. proof of ending your tenancy or selling your home)
Proof of ending a job abroad, if applicable
Proof of terminating any residency based benefits abroad or transferring transferable payments, if applicable
Proof of travel documents such as a one way ticket
Proof of transporting your belongings back to Ireland (e.g. excess baggage fees, removal or shipping receipts)
Proof that your visa for the country you are returning from has expired, if applicable
Proof of closing bank accounts abroad
Proof of opening a bank account in Ireland
Proof of registering to vote in Ireland
Details of family members in Ireland
Any other evidence of intentions to remain in Ireland for good. For instance - letters of support from family members confirming your permanent return to Ireland, proof of renting a property in Ireland, proof of seeking employment in Ireland (both prior to and following your return), proof of enrolling your children in school here, proof of registering with a GP, proof of exchanging your driving licence, proof of joining any local groups …etc.