Conceptually, how is a deferred tax balance actually calculated from the books vs. the tax return?

Deferred taxes are measured on the BALANCE SHEET using the asset/liability (temporary difference) approach under ASC 740: for each item, compare its book (GAAP) carrying value to its tax basis. The difference is a temporary difference; multiply it by the enacted tax rate expected to apply when it reverses. Book basis > tax basis on an asset (or book < tax on a liability) → taxable temporary difference → DTL. Book basis < tax basis on an asset (or a deductible item like a reserve) → deductible temporary difference → DTA. The NET deferred balance is the sum across all temporary differences (plus NOL/credit carryforwards), then reduced by any valuation allowance.