What constitutes allocable overhead for depletion is a matter of professional judgement. For my companies with royalty income, I allocate overhead to royalties vs other income on the basis of gross income, and allocate amongst royalties on the basis of expense. I don't treat ad valorem tax as overhead; I consider it a direct expense of the property the tax is paid on. Tax prep and other sort of "generic" business costs are overhead. Legal fees related to title issues are leasehold costs, not an expense item.