Up front payment to distributor

Hello, I'm needing help in the proper accounting treatment for an upfront payment to a distributor. The contract is between my company and the distributor for a term of three years for the distributor to only sell my company's products to specified territories during this time frame. The distributor will receive a 10% commission based on monthly sales, and the distributor also is receiving a large up front bonus for signing the contract with us (this up front payment is a large reason why the distributor signed the agreement). The contract can be terminated by either party with 30 days written notice, and the up front payment does not get paid back to my company under any circumstances. I keep going back on forth on whether the up front payment may be capitalized and amortized over the three year contract term (and accelerated if the contract is terminated early), or if the full up front payment must be expensed immediately. Capitalization would be preferred, but just want to do what is right. Any and all help is greatly appreciated!! Thank you!!