I Kept Building Personal Finance Prototypes. Eventually I Stopped Pretending They Were Separate.

For a long time, managing your personal finances meant building a spreadsheet.

Not because spreadsheets are good at this. Because nothing better existed. You tracked expenses in one tab, savings rate in another, upcoming costs somewhere else. If you wanted to compare two insurance policies, you opened a calculator. If you needed to work out your tax position, you either hired someone or spent an afternoon on the ATO website hoping you had not missed anything.

It worked. Kind of. If you were diligent enough, patient enough, and willing to rebuild the analysis every single time the question changed.

Most people were not. So most people guessed.

How I realised I had the same problem

I am a software engineer. I manage my own finances. I do my own tax return. I make my own investment decisions.

And for most of last year, I was guessing too.

The moment I realised it was after the financial year ended. I found out — too late — that I had not claimed deductions I was entitled to on hardware I had bought for work. A keyboard. A monitor. A mouse. The purchases were done, the year was closed, and the window was gone.

Not because the rules were complicated. Because I had no system that kept watch.

That is the thing about personal finance decisions: the cost of not knowing is invisible until it is not. The tax deduction you missed. The insurance renewal you accepted without modelling the alternatives. The housing decision you delayed because you could not see how all the variables connected.

The spreadsheet does not warn you. It just records what happened after.

What the tools had in common

When I looked at the three tools I had built, the pattern was obvious in retrospect.

A tax tracker. A car insurance comparison calculator. A personal finance dashboard. Three separate prototypes, all personal finance, all built because something had gone wrong and I wanted it not to go wrong again.

The insight was not that these should live in one product. The insight was what they had in common: each one was solving a problem that a financially literate person could solve with a spreadsheet, but would not, because the setup cost was too high and the moment had usually already passed by the time they got around to it.

That is the gap Finance Watchtower is built to fill. Not a budgeting app. Not a bank dashboard. A system that does the work before you need it — on tax, insurance, spending, and major financial decisions — so that when the moment arrives, you are looking at a clear answer instead of a blank spreadsheet.

The latest module is a housing decision model. The question it tries to answer is: should you buy now, rent longer, or delay? Pull on that thread and it gets complicated fast — your current savings, your timeline, your lifestyle assumptions, whether you might move cities. The housing tool lays all of that out in one place so you can see how the numbers interact with your actual situation, not just the property price.

Who this is actually for

There is a specific person this is for.

They manage their own finances. They do their own tax returns. They are not intimidated by numbers and they are not looking for a tool that simplifies money down to a progress bar. What they want is better analysis, faster — without having to build it from scratch every time.

The tools that exist for this person are either too simple (consumer budgeting apps that assume you just need to track spending) or too manual (a well-built spreadsheet that only works if you maintain it). Neither is quite right.

The cost of that gap is not visible in any single decision. It shows up across a career. The tax deductions you did not claim. The insurance you renewed without modelling it. The major financial decision you made on instinct because you did not have the time to build the analysis properly.

That is the bar Finance Watchtower has to clear. Not "better than nothing." The question is: is this meaningfully more useful than a spreadsheet you built yourself? Because the people I am building for are perfectly capable of building that spreadsheet. They just should not have to.

Every feature has to clear that bar. Most ideas do not.

Where things are now

The personal finance dashboard and car insurance comparison tool are the most mature modules. The housing decision model is under active development.

I am releasing these as modules progressively — not because the product is unfinished, but because I want to know which module someone would pay for in isolation before I commit to a price. That answer shapes everything: positioning, what to build next, where to put the most polish first. My rough sense is around ten dollars a month. But I am not landing on a number until I understand what the core is.

Building in public is part of the strategy, which is why this post exists.

More updates as this develops.