How do I reconcile MonCash transactions with my orders at the end of the day?

Mismatches usually come from four places: payments you never confirmed (customer closed the tab), orders you marked paid without a real payment, fees, and timezone cut-offs.

1. Store MonCash's view of every payment, not just your own

CREATE TABLE moncash_payments (
  transaction_id  text PRIMARY KEY,
  reference       text NOT NULL,          -- the orderId you sent
  amount_htg      numeric(12,2) NOT NULL, -- as reported by MonCash
  payer           text,                   -- phone number (see privacy note)
  status          text NOT NULL,
  seen_at         timestamptz NOT NULL DEFAULT now()
);

2. Run a sweeper every few minutes: for each attempt still PENDING after ~10 minutes, call RetrieveOrderPayment. That catches payments whose customer never came back.

3. Nightly report, in one timezone (America/Port-au-Prince):

SELECT o.id, o.total_htg, m.amount_htg, m.transaction_id,
       CASE
         WHEN m.transaction_id IS NULL AND o.status = 'PAID' THEN 'PAID WITHOUT MONCASH RECORD'
         WHEN m.transaction_id IS NOT NULL AND o.status <> 'PAID' THEN 'MONEY RECEIVED, ORDER NOT PAID'
         WHEN m.amount_htg <> o.total_htg THEN 'AMOUNT MISMATCH'
       END AS problem
FROM orders o
FULL JOIN payment_attempts a ON a.order_id = o.id
FULL JOIN moncash_payments m ON m.reference = a.id
WHERE (o.created_at AT TIME ZONE 'America/Port-au-Prince')::date = CURRENT_DATE - 1;

Rows with a problem are what a human reviews. Everything else should match the portal statement, apart from any fees, which you record separately rather than subtracting from order totals.