Paste an Amazon settlement flat-file (GET_V2_SETTLEMENT_REPORT_DATA_FLAT_FILE). This sums every line item and checks it against the payout total the report declares — and flags the lines with no order id, the ones that silently break reconciliation. It runs entirely in your browser; the file never leaves your machine.
This reads the standard V2 settlement flat-file columns (total-amount, amount, order-id, amount-type, amount-description). It reconciles the declared payout against the sum of line items and surfaces the no-order-id lines — the same first check I run on a real migration. A clean tie-out here is necessary, not sufficient: currency splits, deferred transactions and multi-settlement periods still need care. That deeper reconciliation is the done-for-you part.
When Finances v0 goes dark on 28 Aug and your data starts coming from listTransactions, the fees-with-no-order-id and payout-level matching are exactly where totals drift. I migrate you and make it tie out — in writing, no calls. Approach validated by Amazon's dev team (GitHub issue #5353).