Floating-point deposit checks and credit notes broke our Shopify B2B Net-30 fulfillment holds

When a wholesale buyer places a €2,500.00 order on Shopify Plus B2B with Net-30 payment terms and a mandatory 30% upfront deposit (€750.00), warehouse fulfillment must remain locked in PENDING_DEPOSIT until the full deposit clears.

In production, two subtle bugs routinely break custom Shopify Plus B2B webhook handlers: converting decimal currency strings with IEEE-754 floating-point multiplication (19.99 * 100 === 1998.9999999999998) combined with naive orders/partially_paid triggers, and ignoring post-invoice credit notes when computing remaining wholesale balances.

1. Why IEEE-754 float math and partial SEPA transfers release holds prematurely

Many B2B middleware scripts listen to Shopify's orders/partially_paid webhook and release fulfillmentOrders holds as soon as any non-zero payment arrives, or compare floats like paidAmount >= orderTotal * (depositPercent / 100).

When an enterprise buyer sends a partial SEPA bank wire of €500.00 (50000 cents) against a €2,500.00 (250000 cents) order requiring a 30% deposit (75000 cents), a handler that keys off financial_status === "partially_paid" without verifying integer-cent deposit thresholds releases the warehouse hold €250.00 early. Even worse, IEEE-754 binary floating-point arithmetic introduces 1-cent rounding drift on routine wholesale line items (Math.floor(19.99 * 100) === 1998 instead of 1999), causing deterministic ledger reconciliations to fail audit checks.

2. Post-invoice credit notes, returns, and cancelled wholesale orders

In B2B wholesale, invoices rarely stay static between deposit collection and the Net-15, Net-30, or Net-60 maturity date. Damaged pallets, SKU substitutions, and volume rebates generate credit notes (creditNoteCents) after the initial deposit is paid:

• Credit-note reduction before deposit & balance gates: On a €2,500.00 (250000 cents) order where the buyer has paid €2,000.00 (200000 cents) and receives an €800.00 (80000 cents) credit note, the effective invoice total is effectiveTotalCents = Math.max(0, totalOrderCents - creditNoteCents) = 170000 cents (€1,700.00). Naive scripts that ignore credit notes demand another €500.00 from the buyer instead of marking the order FULLY_RECONCILED and surfacing creditDueCents: 30000 (€300.00 overpayment credit due).
• Cancelled orders with partial deposit refunds: If a wholesale order is cancelled (isCancelled: true) after a €750.00 (75000 cents) deposit was collected and only €250.00 (25000 cents) was refunded, the state machine must lock fulfillmentHold: true under ORDER_CANCELLED and surface refundDueCents: 50000 so finance never orphans unrefunded buyer funds.
• Delinquent Net-Terms expiration: Once nowSec > balanceDueAtSec with remainingBalanceCents > 0, the account transitions deterministically to BALANCE_OVERDUE (b2b_net_terms:overdue_balance) with exact overdueSeconds telemetry.

3. The 5-state integer-cent wholesale reconciliation state machine

Every wholesale order evaluation must operate strictly on safe integer cents (Number.isSafeInteger) across 5 primary wholesale ledger states (plus REFUNDED_OR_CREDITED when effectiveTotalCents === 0):

You can invoke the exact integer-cent reconciler over JSON-RPC 2.0 via our Model Context Protocol (MCP) server (POST https://api.revclamp.com/api/mcp) or REST simulator endpoint:

{
  "jsonrpc": "2.0",
  "id": "net-terms-check-1",
  "method": "tools/call",
  "params": {
    "name": "revclamp_reconcile_b2b_net_terms",
    "arguments": {
      "orderId": "gid://shopify/Order/908812",
      "totalOrderCents": 250000,
      "paidAmountCents": 80000,
      "creditNoteCents": 10000,
      "requiredDepositPercent": 30,
      "paymentTermsDays": 30
    }
  }
}