If you are a property owner, or you are purchasing a property and there are trees nearby, your insurance company or mortgage lender may request a tree mortgage report to assess the liability of these trees.
Trees can cause damage to buildings physically or through subsidence damage. Subsidence is where the soil heaves and shrinks due to tree roots taking moisture out of the soil. This occurs on heavy clay soil. A mortgage report assesses the condition of any trees to ensure that risk is kept within reasonable levels. All parts of the trees are considered in relation to their surroundings and any management or recommendations are provided. 

As with a tree health report, all parts of the trees are inspected:
Base of the tree
The main stem
Branch unions
Around the base of the tree in the root area.

A tree mortgage report also specifically focuses on the effect of trees on properties, and any risk to properties that they may cause. This includes any damage that may be caused by tree or branch failure, and any potential damage that may be caused by the roots. If subsidence is suspected, then a structural engineer may be recommended to give a detailed assessment.