An installment sale is a sale of property where you’ll receive at least one payment after the tax year in which the sale occurs. For example, if you sell your car in November and agree that the buyer pays you half of the price in December and half in January, then the January payment could be considered installment sale income.
Go to this section in Credit Karma Tax: Installment Sale Income
If you make money, or realize a gain, from an installment sale, you may be able to report part of your gain when you receive each payment. Installment method rules don't apply to sales that result in a loss.
You may choose to report all of your gain in the year of sale instead. If you elect out of the installment method, you need to report all of your gain in the year of sale even though you don’t receive all the sale proceeds in that year. You can do this as either Sale of Business or Rental Property or as personal Capital Gains or both, depending on the portion of the property that was for business or personal use.