Just Me and AI: I Built the Hardest Part of the System, the Finance Module

This week I want to talk honestly about what I've actually been doing with AI lately, because it's gone way beyond writing a few lines of code for me.

I took on the riskiest piece of the whole project

I'm building a SaaS system for small restaurants and food businesses, and this week I kicked off the "AI finance module": bank reconciliation, chart of accounts, and auto-generated journal vouchers. Anyone who's worked on finance software knows this is where mistakes are easiest to make and hardest to forgive. Every dollar that moves in or out has to turn into the correct journal entry automatically, match up line by line with the bank statement, and get the GST right.

Here's the thing: on this whole piece, the team is just me.

How I split the work with AI probably isn't what you'd expect

A lot of people think coding with AI means "you say one thing, it writes one chunk." Once I really got into it, I found the most time-consuming part isn't writing code at all. It's spelling out the rules first.

So I started by working with AI to write down the "ground rules" for this module: how the chart of accounts is set up, which events map to which entries, how to keep channel fees consistent, and where bank statement imports tend to go sideways. Once those rules were nailed down, I had AI implement things step by step against them. That way it's less likely to drift off course, and I can review and sign off on each piece as it lands.

In other words, I own the judgment calls and set the rules. AI carries the repetitive, tedious, high-volume implementation work.

It wasn't all smooth: a real bug in production

It didn't all go smoothly. Partway through, the head chef at one of the stores told me that after logging in, the "switch store" option had suddenly vanished. Production issues like this are the most stressful kind. I had AI trace through the code and it pinned the cause down to a change in a permission check that was affecting what showed up in the menu. Once we confirmed it, I fixed it and shipped it the same day.

I also handed a bunch of odd jobs to AI: making new images for the blog and build log on my personal site, batch-exporting dozens of course handouts into cleanly formatted PDFs, and clearing out a backlog of customer inquiries in the marketing inbox. None of these is a big deal by itself, but together they can easily eat a whole day for one person.

My biggest takeaway this week

AI won't make decisions for you. The judgment calls are always yours. But it can carry an amount of execution that one person simply couldn't, and for the first time, "one person doing the work of a whole team" actually feels realistic.

Is there something you've been meaning to get to forever that you've handed off to AI lately? Tell me in the comments. I'll reply to every one.