> For the complete documentation index, see [llms.txt](https://docs.zirodelta.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.zirodelta.com/use-cases/just-in-time-balances.md).

# Money that waits in the right place

**For:** prepaid, school, transit and subscription apps.

## The problem

When people pay in advance, the money sits in a spending balance for days or weeks before it is used. That idle float earns nothing for the person who paid, and in many countries the app is not allowed to put it to work.

## How it works

1. The money paid in advance waits somewhere it is allowed to earn, chosen by the rules of the country: for example a regulated savings or money-market product held in the payer's own name through a licensed partner.
2. Each day, the [Settlement Engine](/modules/settlement-engine.md) moves only what is needed into the spending balance, such as a daily limit.
3. The spending balance stays small, and the experience for the user does not change.

## Modules used

Settlement, Yield, Fiat rails.

## Things to know

* The money stays the payer's. The app does not invest money that is not its own.
* What "allowed to earn" means differs by country, and runs only through licensed partners.

## Status

In development.


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