> ## Documentation Index
> Fetch the complete documentation index at: https://docs.getlago.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Graduated percentage

Select the graduated percentage model if you want to define several percentage tiers. You can also
apply a **flat fee** per tier in addition to the rate.
Note that the **rate** is the only mandatory value. It's particularly useful for fintech charging graduated rates for a feature.

Consider the following example, where each unit represents an API call:

| Tier   | First unit | Last unit | Rate | Flat fee |
| ------ | ---------- | --------- | ---- | -------- |
| Tier 1 | 0          | 1,000     | 1%   | \$200    |
| Tier 2 | 1,001      | 10,000    | 2%   | \$300    |
| Tier 3 | 10,001     | ∞         | 3%   | \$400    |

A first transaction at \$500 would cost (500 units x 1%) + \$200 flat fee = \$205.00;
A second transaction at \$550 would cost \[(500 units x 1%)  + (50 units x 2%)] + \$300 flat fee = \$306.00;
A third transaction at \$4,000 would cost (4,000 x 2%) = \$80.00.

<Tip>
  Unlike the fixed fee, **the flat fee is applied to the entire tier**, rather than per transaction.
</Tip>