Square says you sold one number.
The bank shows another.

The breakdown

Where an unexplained gap usually hides

• Your transfer cutoff. Sales after your batch cutoff ride the next deposit — so "yesterday's sales" and "yesterday's deposit" may not be the same money. Every business's schedule is different (Square's default is 5 PM Pacific, but many set their own, or sync it to store hours). Find yours in the Square Dashboard under Settings → Transfers.
• Weekend batching. On Square's standard schedule, Friday-after-cutoff through Sunday sales land together on Monday — one deposit, three days of sales. Whether that's your setup shows in the same Transfers settings.
• A dispute or hold. A chargeback, or a payment held for review, comes out of the deposit without much fanfare. Check Dashboard → Disputes for anything open around that date.
• A gift card hiding in your sales number. Sales paid with a gift card never deposit — that money arrived when the card was sold. Your sales summary lists Gift card as its own tender line; if you entered the total instead of the Card line, the gap is often exactly those redemptions.
• Refunds from another day. A refund you gave Tuesday can come out of Thursday's money. Reports → Refunds shows the date each one actually processed.
• More than one location or account. Each location batches its own deposits, so one bank day can carry several payouts. The per-location payout report is the only clean way to match them.

Any one of these is explainable. The problem is when nobody's actually explaining them, month after month — that's how books drift from reality while looking perfectly fine.

No pitch. Sometimes the answer is "you're fine." Either way, you'll know.