How invoice numbers work
The financial-year series, the prefix, and why numbers never repeat.
Invoice numbers are not decoration. Under GST a tax invoice needs a number from a continuous series for the financial year, unique within your business. TracEasy issues them for you so that rule cannot be broken by accident.
How a number is built
A number looks like MPK/25-26/00001 and has three parts:
| Part | Example | What it is |
|---|---|---|
| Prefix | MPK | Your business’s short code, between two and six letters or digits. Set when your account is created. |
| Financial year | 25-26 | The Indian financial year, April to March. It rolls over on 1 April. |
| Serial | 00001 | A running count, starting again at 1 each financial year. |
One counter per series
Tax invoices and retail invoices are counted separately. Each has its own running serial within the financial year, and a retail number carries -RI on the prefix so the two can never collide.
| Series | First number of FY 2025-26 |
|---|---|
| Tax invoice | MPK/25-26/00001 |
| Retail invoice | MPK-RI/25-26/00001 |
Rules the app enforces
- Numbers are never reused. Even if an invoice is deleted, its number is gone.
- Numbers cannot be typed. The next one in the series is issued when you generate, so two people billing at once cannot land on the same number.
- The series is fixed once issued. An invoice cannot be moved between the tax and retail series afterwards.
- The year rolls over on its own. On 1 April the serial restarts at 1 under the new financial year.
Note
Want a different prefix? It is set when your account is created — contact us. Changing it mid-year is a decision to take with your accountant, since your series has to stay explainable.
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Last checked against the app on 20 September 2026. Screens change as the product does — if something here does not match what you see, tell us and we will fix the page.