The "Background Check Completion Act of 2025" seeks to enhance federal firearms background check requirements by prohibiting licensed dealers from selling a firearm until the background check is fully completed. It amends Section 922(t)(1) of title 18, United States Code, which governs firearm transfers. A central provision of this bill eliminates the current allowance for a firearm sale to proceed if the background check system has not provided a definitive response within a specified number of business days. Specifically, it strikes the language that sets a maximum time limit for background checks from the Brady Handgun Violence Prevention Act. This change ensures that all firearm transfers by licensed dealers require a completed background check , thereby closing the "default proceed" loophole and preventing sales to potentially prohibited individuals due to delayed responses.