In general, you must report crop insurance proceeds in the year you receive them. Federal crop disaster payments are treated as crop insurance proceeds. However, if you use the cash method of accounting and 2019 was the year of damage, you can elect to include certain proceeds in income for 2020. To do this, check the box on line 5c and attach a statement to your return. See chapter 3 of Pub. 225.
Generally, if you elect to defer any eligible crop insurance proceeds, you must defer all such crop insurance proceeds (including federal crop disaster payments). For details on how to complete lines 5a through 5d, see the instructions for Schedule F (Form 1040), lines 6a through 6d.
For more information see IRS Form 4835 General Instructions.