You can re-import the same statement, or overlap date ranges, as often as you like — Ledger of Alpha won't double-count.
How it decides
- Each imported trade carries a stable identifier derived from its broker execution IDs (or, for mapped CSVs, from its key fields).
- On import, trades that match one already in your account are skipped, not duplicated.
- The preview and import summary tell you how many rows were imported vs. skipped as duplicates.
- The same file into a different account imports in full there — duplicates are checked per account.
- A backup you exported carries each trade's identity too, so restoring it onto the same account adds nothing.
Your edits are safe
Because matching trades are skipped rather than overwritten, any journaling, ratings, or notes you added to an existing trade are preserved through a re-import.
A trade you logged yourself
A trade you typed in by hand has no broker identifier, so the check above can't see it. A broker sync compares it a second way: same account, symbol and side, the same size, an entry price within a few cents and an entry date within a day. If exactly one of your trades fits, the synced trade is merged into it instead of being added again. See A synced trade showed up twice, or at the wrong time.