I have a new client where I discovered they paid for a large remodel that is on their books but was never added to their tax return depreciation table. This causes a problem not only for depreciation expense missed, but more importantly the properties basis is way too low based on the remodel they paid for. I would like advice on how others would handle this situation. They should get credit for the large remodel that was missed in prior years so that when they sell they don't have the incorrect gain amount. 

Just to clarify: Property A was bought in 2018 and was added to the tax return for depreciation and basis, Property A's large remodel (also in 2018) was never added to the tax return. How do we get the remodel on the tax return so the basis is correct.