That means building a simple verison first that still fulfills the purpose while not being perfect or polished. Then iteratively improve it to what you and the customer ideally want.

That way, if the deadline comes before you're done, you at least have a working version that fulfills the basic need and allows the kind of workflow that's necessary, even if it still has some rough edges or even gaps in rarely used areas.

Of course this approach requires you to write your contracts in a way that doesn't tie you down too strictly on how exactly things will be solved.