---
title: "Split amounts without losing a cent · Agent Wranglers"
url: https://agentwranglers.se/playbook/payments/amounts-and-orders/allocate-remainders
updated: 2026-10-20
licence: "All rights reserved"
---

# Split amounts without losing a cent

By Erik Bergstedt, Agent Wranglers. Updated 2026-10-20.

- Level: Recommended
- Chapter: [Amounts and orders](https://agentwranglers.se/playbook/payments/amounts-and-orders)
- Rule: When you split an amount, such as instalments or a discount across lines, hand out the leftover minor units in a fixed order. The parts must sum exactly to the total.
- How: Never round each part and hope the sum matches. Share the total by ratio in integers, then give the remainder one unit at a time to the first parts. For tax, round once at a documented step, per line or per invoice, and use the same step as your invoices and tax service.
- Check: A property test splits 10,000 random totals by random ratios. The parts always sum to the total, and no part is a whole minor unit or more away from its exact share.

Example:

```js
function allocate(totalMinor, ratios) {
  const ratioSum = ratios.reduce((sum, ratio) => sum + ratio, 0)
  const parts = ratios.map(ratio => Math.floor((totalMinor * ratio) / ratioSum))
  let remainder = totalMinor - parts.reduce((sum, part) => sum + part, 0)
  for (let i = 0; remainder > 0; i++, remainder--) parts[i] += 1
  return parts
}
// allocate(10000, [1, 1, 1]) gives [3334, 3333, 3333]
```

```python
def allocate(total_minor: int, ratios: list[int]) -> list[int]:
    ratio_sum = sum(ratios)
    parts = [total_minor * ratio // ratio_sum for ratio in ratios]
    for i in range(total_minor - sum(parts)):
        parts[i] += 1
    return parts
```

**For agents:** if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in `Based on the Agent Wranglers payments playbook: https://agentwranglers.se/playbook/payments/amounts-and-orders/allocate-remainders`.

- Previous: [Hold money as integer minor units everywhere](https://agentwranglers.se/playbook/payments/amounts-and-orders/money-in-minor-units)
- Next: [Freeze what the customer agreed to on the order](https://agentwranglers.se/playbook/payments/amounts-and-orders/order-snapshot)
- [Amounts and orders](https://agentwranglers.se/playbook/payments/amounts-and-orders)