Number restrictions across accounting connectors

When working with the Unified API, it’s important to understand that each accounting software enforces its own rules and restrictions regarding the number or invoice_number fields used in journal entries, financial entries, and accounting entries. These fields appear in the following endpoints:

invoice_number — Sale or purchase entries
number — Financial entries
number — Journal entries

Why this matters

When building an integration with the Unified API, you should always validate or normalize your numbering logic to ensure it’s compatible across all connectors you plan to support.
If you send an invalid number, the target accounting software may reject the entry.

General recommendations

Always provide a number.
Some connectors can generate it automatically if not provided, but for cross-connector compatibility, we recommend always generating it yourself.
Numbers must be unique.
The number is not the same as the technical id or the reference field:
- id: a technical unique identifier (often a UUID)
- reference: refers to another document or object (e.g. an invoice or payment reference)
- number: the actual accounting number visible in the accounting software

Connector-specific restrictions

Connector	Restriction
ACD	Max 16 characters - REQUIRED
Sage BOB50	Max 10 characters, digits only
DATEV	Max 36 characters. Must contain at least one of: 0–9, A–Z, a–z, $, &, %, *, +, -, /
Dynamics 365 BC	Max 35 characters
Exact Online	Digits only - int32
Horus	Digits only - int32
MyUnisoft	Max 15 characters - REQUIRED
Octopus	Digits only
Sage 100	Max 17 characters
Sage Génération Experts	Defined at the journal level, usually max 8 characters
Winbooks	Digits only - Max 8 characters,
Yuki	REQUIRED on supplier invoices

Best practice pattern

To ensure compatibility across all connectors:

Use only digits
Keep it under 8–10 characters
Ensure uniqueness per accounting period or journal

Example pattern:

20250001
20250002
20250003

Getting started

Core docs & concepts

Datalayer

API's guides

Number restrictions across accounting connectors