Sinking funds are how VaultRule stays calm. They turn “not monthly” costs into small monthly Vault lines so they stop draining Flow.
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What a sinking fund is (VaultRule definition)
A sinking fund is a planned future expense you save for monthly inside Vault. Not an emergency. Not a surprise. Just predictable.
If you’re unsure what belongs in Vault vs Flow, use: Vault vs Flow: What Counts as a Bill.
The 3-step method
- Pick 3–6 categories that keep surprising you (start small).
- Monthly amount = target ÷ months (annual costs ÷ 12).
- Add the total to your Vault target (then it runs automatically).
Vault math here: How to Calculate Your Vault Amount.
Sinking fund examples (copy these)
| Sinking fund | Target | Timeline | Monthly amount |
|---|---|---|---|
| Car maintenance | €600 | 12 months | €50 |
| Tyres / big service | €800 | 24 months | €33 |
| Travel | €1,200 | 10 months | €120 |
| Gifts | €360 | 12 months | €30 |
| Home repairs buffer | €500 | 10 months | €50 |
Tip: don’t chase perfect numbers. Pick numbers that stop “random” costs from hitting Flow.
Annual bills vs sinking funds
If it’s a fixed annual bill (insurance, fees), track it as an annual bill first: Annual Bills Checklist. If it’s a predictable cost but not a bill (car, travel, gifts), it’s a sinking fund.
Gray zone rule (when you’re not sure)
- If it’s predictable and you’d hate it to hit Flow, make it a sinking fund in Vault.
- If it’s optional or highly variable, keep it in Flow.
Use this guide when you’re unsure: Vault vs Flow: Gray Zone Expenses.
Make it automatic
The simplest setup: include sinking funds inside your Vault target, then automate the payday transfer so it happens without effort.
Steps: Automate VaultRule on Payday.
Your next step
Ready to build the full system?