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The number of customers you can add to QuickBooks Online has no actual limit. If you have tens of thousands of customers, though, you may have experienced performance issues. The more data you have, the longer the software will take to open pages. For further information, please see this article: Why is my QuickBooks Online slow?.
Let me include the following resources to assist you in managing your customer list in QuickBooks Online:
In addition, you can check out this material if you plan to invoice your customer so they can pay later:
If you have any additional questions about managing your customer's list, please don't hesitate to ask in the Community. We're always available to assist you.
