Entrepreneurs run rolling cashflow forecasts to spot trouble years ahead. I applied the same model to private budgeting.

I checked my budgeting app last Sunday morning. It told me I had spent 12% more on groceries than the month before.

Useful. But completely irrelevant to the question I actually needed to answer: can we afford to make an extra mortgage payment in Q3?

No app I tried could answer that. Nor could the spreadsheet I’d been halfheartedly maintaining since 2019 answer this question.

The Problem

Every personal finance tool I know is built around tracking. Those tools all follow the same model: Connect to your bank, categorize your spending, and get a colorful pie chart of where the money went.

To answer the mortgage repayment question, that’s the wrong model.

You’re not trying to figure out where last month’s money went. You’re trying to answer questions like:

  • If interest rates rise by 1% at renewal, what does that do to our cash position in 18 months?
  • We want to pay off the mortgage 4 years early — can we absorb an extra 800 per month starting in September?
  • The roof needs replacing. Does that kill our liquidity, or can we absorb it?

Tracking apps answer none of these. They’re excellent rear-view mirrors and useless windshields.

The Solution

I’m the Founder & CEO of Yonder, a B2B SaaS company. Since incorporation, I have been maintaining a detailed cashflow forecast in Excel. Over time, this tool morphed into a rolling 36-month cashflow forecast.

We can see a cash crunch coming two years out and adjust. We model scenarios before committing to headcount or infrastructure costs.

Three years ago, I rebuilt my household finances with the same approach. The system has three components:

  • A dynamic 3-year forecast. Not a static budget, but a living model where every change ripples forward automatically. If my wife gets a raise in March, I see the effect on our liquidity through the next two years in seconds.
  • A scenario layer. Mortgage payoff options, income changes, large unplanned expenses — I model them before they happen, not after.
  • A 30-minute monthly ritual. Not a weekend project. Enter actuals, check the chart, and adjust one or two assumptions if needed. Done.

I’ve packaged the whole system into a playbook called The Household CFO. It’s the third version of a guide I’ve been publishing since 2023. This edition adds two new chapters: one on mortgage payoff strategies, and one on running household finances as a couple.

What’s included in this playbook?

  • A 10-chapter PDF guide covering the full system, from first setup to advanced scenario planning
  • The Excel template with 24 tabs, pre-wired formulas, and a dashboard that updates dynamically

The playbook and template are available on Gumroad – get it here!