---
title: "Switching billing apps without losing what people owe you"
source: https://www.lskhata.com/blog/switching-billing-apps-without-losing-balances
category: "Getting started"
language: en
published: 2026-08-14
reading_time: 7 min
---

# Switching billing apps without losing what people owe you

_How to move to a new billing app mid-year: what to carry over, what to leave behind, and the week where you keep both._

## In short
- Carry balances, not history. Every customer's current outstanding becomes an opening balance in the new app.
- Keep the old app readable for a month. Do not cancel it the day you switch.
- Move at a quiet point in your month, not at the end of it, so the first reconciliation is small.
- Check the new outstanding total against the old one before you trust it. One number, two apps — they should match.

Switching billing apps has one genuine risk and a lot of imagined ones. The genuine risk is that the money people owe you arrives in the new system wrong, and you do not notice for two months. Everything else — losing old bills, missing reports, having to re-enter products — is either recoverable or not actually a problem.

_[Figure: The same rule as moving off paper: carry the balances, leave the history where it is, and keep the old record readable until the new one has proved itself.]_

### Carry balances, not history

The temptation is to re-enter a year of transactions so the new app has "everything". Resist it. It takes days, it is dull enough that most people abandon it halfway, and the result is a second copy of records you already have. What you actually need going forward is each customer's correct starting position.

So for each customer who owes you anything, create them in the new app with their current outstanding as an opening balance. Customers at zero do not need to be moved at all — they will be created the next time they buy something on credit.

**Do the same for your suppliers.** People remember to move customer balances and forget party balances. What you owe a supplier is money too, and starting a supplier ledger at zero when you owe them forty thousand rupees produces a very cheerful and completely wrong picture of your position.

### The week itself

1. **Pick a quiet day, mid-month** — Not the 1st, and not the last week. You want a fortnight of ordinary trading before anything monthly depends on the new numbers.
2. **Export or write down every outstanding balance from the old app** — If it exports, export. If it does not, a photograph of the outstanding list is enough — you only need it while you type.
3. **Enter your ten largest debtors first** — They are most of the money. If you stop after ten, you have already moved the majority of your exposure, which makes the rest of the job optional rather than urgent.
4. **Add the rest as they walk in** — The same approach that works when moving off paper. Somebody buying on credit gets created with their opening balance at that moment, during a transaction that was happening anyway.
5. **Compare the two totals** — Total outstanding, old app against new. They should match. Do this before you stop looking at the old app, not after.

### What not to bother moving

| Leave behind | Why |
| --- | --- |
| Individual old transactions | The old system is still the record of them. Duplicating that record does not make it truer. |
| Customers at zero balance | They add nothing to the ledger and slow the move down. They get created on their next credit purchase. |
| Products you no longer stock | A migration is a free opportunity to drop the dead half of your catalogue. Take it. |
| Old reports | Export any you actually want as PDF or CSV and keep the file. You do not need the new app to regenerate history it never had. |

**Do not cancel the old app on switch day.** Keep it readable for a month. It costs you very little and it is the only thing that answers a question about a transaction from before the switch. People who cancel immediately usually discover within a fortnight that they needed to look something up.

> A migration is not finished when the data is in. It is finished when the two totals agree and you have stopped checking.

## Common questions

**Will I lose my transaction history if I switch billing apps?**

You will not carry it into the new app, and you generally should not try. What you carry is each customer's current balance as an opening balance. The old app or your old books remain the record of everything before the switch, which is why you keep access to them rather than cancelling immediately.

**How long should I run both apps at once?**

About a month, and only in the sense of keeping the old one readable. Actually entering every sale twice is exhausting and people give up within days, at which point you have two half-correct records. Bill in the new one, keep the old one for looking things up.

**When in the month is the best time to switch?**

A quiet stretch, not month end. Switching on the 1st sounds tidy but it collides with whatever monthly reconciliation you already do. A mid-month Tuesday gives you a fortnight to find problems before anything depends on the numbers.

**How do I check the move worked?**

Add up total outstanding in the old app and in the new one. They should match to the rupee. If they do not, the difference is almost always a customer you missed or a balance typed with a digit transposed, and it is far easier to find on day one than in three months.