When a Customer Disputes an Invoice You Both Agreed To

You finished the work, sent the invoice for exactly what you quoted, and now the customer is pushing back. Maybe they say the price was different, or the work wasn't up to standard, or they just want to negotiate as though the job never started. This is the point where most side hustle contractors either cave to get paid something or dig in and lose the relationship entirely, when the real answer is almost always a structured middle path that protects what you're owed without torching months of effort. The short version: document everything, respond in writing, don't accept partial payment without conditions, and know when the dispute has crossed from annoying into small claims territory. People don't usually set out to stiff you.