You need to be sure of what's going on here before you sue anyone. Can you dispute the charged credits with the credit card processor so that they'll investigate the transactions? Can they block this card from further credits?
Whether or not the credit card processor will help, you need to confront your partner. If your partner admits responsibility, report this to the police. Whether or not the police consider this a civil matter, if your partner has been stealing from the business, you need to end this partnership. You can sue for dissolution of the partnership, breach of fiduciary duty, conversion, and for an accounting, among other claims. If you have a written partnership contract, you may have restrictions on your rights and/or other remedies, so you need to hire a business litigator to review your contract and pursue your claims as applicable.
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My colleague is correct. This also could be an employee, an ex-employee or someone who has accessed your login information. If no purchases have been made, then the thefts are being made from the credit card owner. Are the funds being deposited into your parntership bank account? Is your partner withdrawing them?
Disclaimer: The response given is not intended to create, nor does it create an ongoing duty to respond to questions. The response does not form an attorney-client relationship, nor is it intended to be anything other than the educated opinion of the author. It should not be relied upon as legal advice. The response given is based upon the limited facts provided by the person asking the question. To the extent additional or different facts exist, the response might possibly change.
You can sue for dissolution, conversion, breach of fiduciary duty and for an accounting. Check with a lawyer in your locale to discuss more of the details. You might find my Legal Guide helpful "Ethics: Yes I Need a Lawyer!"
Good luck to you.
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