There are special IRS tax rules you should be aware of it you engage in an installment sale of multiple assets in one transaction. This generally involves real estate

The sale of unrelated assets of the same type in a single sale contract is reported as one transaction under the installment method. If any of the assets are sold at a loss, however, those items cannot be reported under the installment method and therefore must be reported separately; the remaining assets are reported together. In order to figure the gain/loss on each asset, the seller must allocate payments received among the various classes of assets sold. The allocation is computed using the ratio of each asset’s FMV to the total selling price less mortgage assumed.

If the assets are mortgaged and the mortgage is assumed or the asset taken subject to it by the buyer, use the FMV of each asset, net of mortgages assumed or taken subject to, in order to make the allocation.