You will have to create the transaction manually Select Transactions > Add Transactions > In the Account tab (which is located between Type: and Tax year) select Cash > enter date, description amount, in the select a category select business income > save
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Thank you for this clear answer @Charies_M . There seems to be a lot of confusion in the community about cash income/expenses for QBSE users, but this addresses it head on. I'd love for that option to be available in the near future. My client would be ever so grateful.