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Was it actually a lease? Rental income is ordinary income reportable on Schedule E (Part 1), not capital gains.
yes it was a 1 time payment unless they find natural gas on the property
Upfront bonus payments for oil & gas property leases are considered "Advance Royalties" and as stated above are reported on Schedule E as Rent & Royalty income. No depletion deduction is allowed & the income is taxable in the year received.
You would be entitled to any expenses related to the property or the lease; real estate taxes, legal expense or anything else directly related to the land or the lease.