Go to Transactions > Troubleshooting > Resolve Possible Duplicates

LessAccounting tries to identify possible duplicate transactions based on date and amount. We make it easy to choose which transaction to keep and which to delete. In some cases it's purely a coincidence that you deposited or spent the exact amount of money on the same day for 2 different things. In those cases, feel free to just "Keep" both.

Deleting duplicates will help keep your balances in check.