Quick Answer
If you win a small-business set-aside, there's a rule that limits how much of that work you can hand off to a subcontractor. For most services and supply contracts, you can't pay outside subcontractors more than 50% of what the government pays you for the job. A lot of contractors have heard this as "51%." That's not right, and getting it wrong can put your award at risk. The good news: once you understand how it's actually calculated, it's very manageable to stay on the right side of it.