Is Seller Ledger double-entry accounting software?

It is. However, to make the software easier to use for small business owners, we hide a lot of the balance sheet and double entry mechanisms from the interface.

But, here are some examples to demonstrate how you can tell there is double entry accounting behind the scenes:

1. Sales and expenses from connected marketplaces like eBay, Amazon, Etsy, etc show up within an "account" for each of those marketplaces, which we place on the client's dashboard, complete with a balance.
2. All of the sales and expenses from connected marketplaces are included in profit and loss calculations. But payouts from those marketplaces are treated as "transfers". In fact, if your client links the bank account that receives those payouts, you will similarly see those deposits treated as "transfers" and not impact profit and loss calculations.
3. If you click into any bank account or credit card and try to change the category, you can scroll down to see options to classify them as "Transfer: xxx" where xxx us the name of another account. These will always be balance sheet accounts. And, in fact, you will see an option for "Transfer: Non-connected account" - this can be used for cases where a client has chosen not to link another account.

We are working to expose more of the balance sheet, journal entries and such to accounting professionals, so stay tuned.