If you sell on credit, you already keep a book — on paper, in your head, or in a spreadsheet. What you need from software is the same job, not a tax package.
What you actually need today
Names. A credit sale. A payment. A number you can open on the phone when someone asks. Full accounting software usually starts with stock, invoices, and a chart of accounts. That is a different job. You can add it later if a bank or a partner asks.
Until then the question is still: who owes you, and can you show it without arguing?
Kaymn is that customer book in the browser — not kaymn.com, not invoicing, not a till. Try it for 7 days.
