Understand what a chargeback actually is, since it is not a refund request. The customer has gone to their bank rather than to you, the money is removed from your account immediately, and you are asked to prove the transaction was legitimate. You may also pay a fee whether or not you win, which is why prevention matters more than the defence.
Gather the evidence rather than writing an account of what happened. Proof of delivery or completion, the signed agreement or accepted quote, the communication history showing what was agreed, your published terms including the refund policy, and any record showing the customer used what they bought. Documents persuade in this process and narrative does not, because the decision is made by somebody applying rules rather than reading a story.
Respond even when you expect to lose, because undefended disputes affect your standing with the processor beyond the individual case. A rising dispute rate can result in higher fees, held reserves, or termination of your merchant account, and the rate is calculated on disputes rather than on outcomes.
Contact the customer directly in parallel, and quickly. A meaningful share of disputes come from genuine confusion rather than an attempt to avoid paying: an unrecognised name on the statement, a family member who made the purchase, or somebody who could not find how to request a refund. Many of those can be withdrawn if you reach the person, and a resolved dispute is considerably cheaper than a won one.
Then work out how it happened, because most causes are preventable and repeat. The most common is a statement descriptor the customer did not recognise, which is a setting in your processor and takes minutes to correct. After that come unclear refund policies, delivery timelines that were not stated, and a customer who could not find how to contact you and went to their bank instead.
Make yourself easy to reach, which is the single most effective prevention. A visible phone number and a monitored email mean an unhappy customer complains to you rather than to their bank, and the difference in cost between those two paths is substantial.
Keep the records that make defence possible as a matter of routine rather than assembling them under pressure. Delivery confirmation, written acceptance of the work, and the terms the customer agreed to. A business that has those filed per transaction can respond in twenty minutes, and one that does not spends a day reconstructing and frequently cannot.
Watch the pattern rather than the incident. One dispute is an event. Several in a quarter is information about how you describe what you sell, what your terms say, or how reachable you are, and addressing that is worth considerably more than winning any individual case.
Check your descriptor now rather than after a dispute, since it takes minutes and is the single most common preventable cause. Search your own business name and see what a customer would recognise, and set the descriptor to your trading name rather than a company name nobody has encountered.
Set a clear refund policy and place it where somebody sees it before buying, because a customer who knows how to obtain a refund uses that route rather than their bank. The cost of an occasional refund is considerably lower than the fees, the lost revenue, and the effect on your standing that a dispute carries.