What is Deferred Acquisition Costs?

Legal Definition
Deferred Acquisition Costs (DAC) is a term commonly used in the insurance business. It describes the practice of deferring the cost of acquiring a new customer over the duration of the insurance contract. Insurance companies face large upfront costs incurred in issuing new business, such as commissions to sales agents, underwriting, bonus interest and other acquisition expenses.

DAC under U.S. GAAP, MSSB (Modified Statutory Solvency Basis) and IAS 39 are all very similar, except that IAS 39 only allows direct, incremental costs to be deferred rather than all acquisition costs.
-- Wikipedia
Legal Definition
Holding off on paying costs about insurance until a legal agreement is signed.