Projects rarely overrun because the code was hard. They overrun because the specification was vague, and every ambiguity turned into a change request halfway through the build.
What we do
We sit with the people who do the work, map the process as it really runs, and write it down: every screen, every state, every business rule and every integration point. Edge cases are decided on paper, where they are cheap, rather than in development, where they are not.
What you get
A specification a development team can quote against with confidence, a realistic scope, and a document that keeps stakeholders aligned once the build starts.
Less rework, and a launch date that survives contact with reality.