How do you account for shared costs by another company when building a fixed asset?

When accounting for shared costs incurred by another company in building a fixed asset, you should first determine the nature of the shared costs and ensure they directly relate to the asset's construction. Allocate the appropriate portion of these costs to the asset based on a reasonable basis, such as usage or benefit derived. Record these costs as part of the asset's capitalized costs on the balance sheet. Finally, ensure compliance with relevant accounting standards, such as IFRS or GAAP, regarding joint costs and fixed asset capitalization.