If you buy a stairlift you may be able to claim the VAT back. This does not apply to a rental stairlift.
From Revenue.ie:
You may reclaim Value-Added Tax (VAT) on certain aids and appliances for use by persons with disabilities. The relief applies to VAT on the purchase of aids and appliances designed to assist persons with disabilities.
These aids and appliances are used by such persons to assist in the performance of daily functions or in the exercise of a vocation. The relief is not allowed on services or on the rental of goods.
You can download the most up to date version of VAT form 61A as a PDF here.