I Used Spreadsheets for Years. Here's Why I Stopped.

I want to be upfront: I'm a software engineer by trade. In some of my early jobs they called me the King of Excel. If anyone should be able to make a spreadsheet work, it's me. And for years, I did make them work. I'd tried Quicken and Peachtree back when I had a property in the US - proper accounting software, but way too complex for tracking a rental. So when I started letting in NZ, I went back to basics: Excel first, then GnuCash for a while, then back to spreadsheets. Across four apartments at 135 Hobson St in Auckland CBD - a three-bedroom, two one-bedrooms with car parks, and a one-bedroom - tracking rent from multiple rooms at different rates, partial payments, late payments, car parks - all in a series of tabs and formulas.

It worked. Until it didn't.

Three Rooms, Three Rates, One Spreadsheet

I rent rooms individually in a three-bedroom unit. Room one at $320 a week. Room two at $240. Room three at $200. Plus a car park at $60. That's $820 a week total, coming from three different people into my bank account at different times, in different amounts.

Every week, I'd scan internet banking and try to match each payment to a room. Tenant A usually paid on Monday. Tenant B paid fortnightly. Tenant C paid whenever they felt like it.

I had a spreadsheet with a tab for each room, colour-coded: green for paid, yellow for partial, red for overdue. It looked professional. I was honestly a bit proud of it.

But maintaining it took fifteen to twenty minutes every Sunday. And that was on a good week.

What I Missed

The thing about spreadsheets is that they only know what you tell them. They don't watch your bank account. They don't flag anomalies. They just sit there, waiting for you to type in the next row.

Here's what slipped through on me:

Partial payments that I didn't chase. A tenant pays $200 instead of $240. I note it, intending to follow up. Next week, they pay $240. Both entries recorded. But I'm still $40 short, buried in a column I'd only notice if I checked carefully. Over six months, those shortfalls added up to hundreds of dollars I never recovered.

Late payments that became a pattern. One tenant was consistently two or three days late. Not enough for alarm bells any given week. But those few days stretched to a week, then two. By the time I realized, they were significantly behind.

Rent increases that didn't stick. I sent the 90-day notice, the date came and went, the tenant kept paying the old amount. Took me three weeks to notice because the payment still showed up as a regular deposit - just $20 less than it should have been.

Room turnover chaos. Tenant moves out, new one moves in at a different rate. Update formulas, adjust expected amounts, carry over balances correctly. Every room change was twenty minutes of careful spreadsheet surgery.

And then there are the situations no spreadsheet can warn you about. I once rented a three-bedroom to individual strangers. One young woman gradually bullied the other two out, then helpfully offered to find replacements. I agreed, but weeks went by with excuses and no one moving in. She was paying a middle-room price but had the whole apartment to herself. Eventually I discovered the truth - she was listing the other two rooms on Airbnb as the host, pocketing the money. More than enough to cover her own rent. She'd also refused to pay a bond at the start, and I'd foolishly agreed. I had her out within two weeks. The real disaster would have been if Council had found out - and they do check online listings - because my rates would have gone up threefold to commercial rates. Lesson learned: always take a bond, always verify what's happening in your property, and be very careful renting rooms to strangers who don't know each other.

These days when I rent the three-bedroom, I rent to a group - usually students who already know each other. I interview them together. I ask about trust, how they share chores, who does the vacuuming, the dishes, the rubbish. I suggest how to split the rent based on room size and convenience - the master bedroom has an ensuite, the smallest room is tiny with no window, so the split reflects that. Power, water, and internet they divide equally.

The key thing: all three sign one tenancy agreement with joint and several liability. That means each tenant is responsible for the full rent, not just their share. If one person leaves, the other two owe the total rent until they find a replacement. I don't chase three people for three amounts any more. One tenancy, one rent figure, one bond. If someone leaves, it's on the group to find a flatmate, not on me to find a new stranger. It's simpler for everyone and my spreadsheet days of tracking three rooms at three rates are over.

Tax Time Was the Worst

At the end of the financial year, I needed total rental income per property for my accountant. Sounds simple. It wasn't.

I had to go tab by tab, summing actual payments for each room, accounting for partial payments and mid-year rent changes. If the spreadsheet had gaps - and it always had weeks where I'd been busy or on holiday - I'd have to reconstruct from bank statements. Cross-referencing three months of transactions at 10pm the night before the tax deadline is not how I want to spend my evenings.

IRD expects accurate records. Under-reporting rental income is a compliance issue. Over-reporting means you pay tax you don't owe. Getting the number exactly right from a manually maintained spreadsheet across multiple rooms was genuinely difficult.

The Tribunal Moment

The breaking point came when I had to take a tenant to the Tenancy Tribunal for $1,150 in rent arrears. The Tribunal wanted an arrears schedule - week by week, what rent was due, what was paid, with partial payments allocated to specific periods.

I had to build this from my spreadsheet and bank statements. It took me an entire evening. Going through months of transactions, matching each deposit to a rent period, accounting for the partial payments, making sure the running total was correct. And then double-checking the whole thing because I knew the adjudicator would scrutinize it and the tenant would dispute it.

I got through it. The Tribunal accepted my schedule and I won the case. But sitting there at midnight, building an arrears schedule from a patchwork of spreadsheet tabs and bank statement PDFs, I thought: there has to be a better way.

That was the night I started thinking about building something purpose-built.

The Real Cost of "Free"

A spreadsheet is free. That's its biggest selling point and its biggest trap. For a single property with a single tenant who always pays on time, a spreadsheet is genuinely fine. Five minutes a week, no drama.

But for me, with three rooms at different rates, partial payments, tenant turnover, and the occasional problem tenant - the spreadsheet was costing me real money. Not just my time (though two hours a month at any reasonable hourly rate adds up to hundreds a year). The missed partial payments. The rent increase I didn't notice wasn't being paid. The stress and time of building a Tribunal-ready arrears schedule from scratch.

The spreadsheet wasn't free. It was just hiding its costs.

From Spreadsheets to GnuCash to Building My Own

I tried GnuCash for a while. Solid software - double-entry bookkeeping, proper reconciliation. But it's built for general accounting, not rental management. It doesn't know what a tenancy is. It doesn't know that $240 on a Tuesday is Room 2's rent, or that it was due Monday. I was still doing all the matching in my head. GnuCash was just a fancier place to record the result.

That's when I started building RentManager. Not because I wanted to build software - I do that all day at work. But because nothing understood my specific problem: multiple rooms at different rates, bank transactions needing matching to tenancies, arrears tracking per period, and tax reports from actual matched payments.

Rent schedules per room with effective dates, so rent increases track automatically. Bank transaction import and matching based on amount and sender. Arrears calculated in real time, period by period, with partial payment tracking. The arrears schedule I spent an evening building by hand for the Tribunal? One click now. Seconds, not hours.

If This Sounds Familiar

If you're a landlord sitting there on a Sunday afternoon, updating a spreadsheet with this week's rent payments, wondering if that $50 shortfall from three weeks ago ever got sorted - I built this for you. Specifically, I built this for me, and then realized there are thousands of landlords in New Zealand doing exactly the same thing.

RentManager is built for small landlords who just want the admin done without the hassle. One property or ten - it doesn't matter. Import your existing data via CSV so you're not starting from scratch. Connect your bank account and let automatic matching do the weekly reconciliation. Arrears show up on your dashboard the moment they happen, not next Sunday when you get around to checking. Tax summaries at year end. Tribunal-ready arrears schedules if you ever need them.

Plans start at $9 a month.