How does a party prove the other side acted in bad faith to justify a costs award?

Proving bad faith for costs purposes generally means showing a pattern of conduct that goes beyond ordinary hard-fought litigation — things like deliberately withholding or misrepresenting financial disclosure, bringing motions or applications known to lack merit specifically to cause delay or expense, ignoring court orders or deadlines without justification, or using the litigation process itself as a tool to harass or wear down the other party rather than to genuinely resolve a dispute. A single tactical misstep or a losing argument made in good faith generally isn't enough on its own.

Evidence typically comes from the court record itself: comparing what was disclosed against what should have been, tracking missed deadlines and unexplained delays, and documenting specific steps that had no real legal basis. Because courts distinguish between aggressive-but-legitimate advocacy and genuine bad faith, a costs argument along these lines needs to be built on a clear, well-documented pattern rather than framing every disagreement as bad faith, which tends to undermine the argument rather than support it. Anyone pursuing this kind of costs argument should work with their lawyer to build the record carefully throughout the case, not just at the end.