Both are cloud invoicing tools within the TeamSystem ecosystem, but they have different focuses. Billin targets freelancers and micro-businesses looking for a very lightweight solution to issue invoices and manage payments. Quipu adds the pre-accounting layer connected to the accountant, making it more suitable when an external practice needs direct access to the client's data to close the books. If the business is simple and there is no external accountant involved, Billin may be sufficient; if that collaboration exists, Quipu delivers more value.