Can I go back and enter older inventory if I already entered a Beginning of Year balance?
Even if you entered a Beginning of Year balance, you can still go back and enter more older inventory. It will change the corresponding "Beginning" and "Current" balances, but you can then either edit the prior adjusting purchase transaction, or delete it and enter a new one.
Let's take an example:
Assume you are a new Seller Ledger customer starting in the middle of 2023. In your 2022 tax return, you reported an ending inventory balance of $800. So, following the steps to get set up properly in Seller Ledger, you entered that amount with a date of 12/31/22.
Now, let's say you're going through some old receipts (or perhaps a reasonably well maintained spreadsheet,) and find some items that you purchased in 2022 that you'd like to track. Let's say one of those purchases was from May 5, 2022 and the item, which we'll call "blue widget #2", cost $5.99.
Just click the "Add inventory" button, enter the purchase details, including date, amount, product name and (optionally) SKU, and click save. Now, you will see the Ending Balance from 2022 change from $800 to $805.99, which no longer matches the count your did last year (or what you filed) on your tax return. To fix this, you can either edit the 12/31/22 entry of $800 and change it to $794.01, or you can delete it altogether and re-enter a new transaction for $794.01. Either approach will result in getting you back to the correct End of Year balance of $800.