Ameliorative waste describes physical alterations made by a tenant or life tenant that improve, rather than damage, the land or buildings, but still interfere with the reversioner’s or remainderman’s rights. It commonly arises in landlord and tenant, trusts of land and real property disputes. Unlike permissive or voluntary waste that causes deterioration, ameliorative waste increases the property’s value, for example by changing the character of a house or estate to suit modern commercial use. The key issue is not financial loss but substantial alteration of the property’s nature contrary to the terms of the lease, trust or title, or contrary to the intentions of the person entitled in reversion. In England and Wales, Northern Ireland, Scotland and Ireland, the concept is largely derived from case law and general principles, rather than detailed statutory definition. Courts may grant damages or injunctions where alterations amount to prohibited waste, depending on express covenants, reserved powers of alteration and the parties’ reasonable expectations. In practice, modern leases and trust instruments often regulate structural alterations expressly, reducing the need to rely on the traditional doctrine of ameliorative waste, but the concept still informs interpretation of quiet enjoyment and repair obligations.