Yes, under IFRS, a lessor can record a liability for unearned rentals and a receivable for advance payments made by a tenant under a legal contract. The accounting treatment would be to recognize the advance payment as a receivable and income for the current period, and to recognize the unearned portion as a liability. This is in line with the principle of revenue recognition, which states that revenue should be recognized when it is earned, and not when it is received.