# Numbering and billing details

> Your legal details on every document, and the numbering circles that keep invoice numbers gapless.

## Billing details

Under **Settings → Billing**, enter your legal company name, address, VAT ID and bank details. They are frozen onto every invoice at finalization, so a later change never alters an invoice already out. The **Agency country** under Settings → General decides which VAT rules and which billing profile apply: Germany, Austria or the United Kingdom.

## Numbering circles

Invoice numbers must be gapless. A numbering circle defines the prefix and the counter, for example `INV-2026-` starting at 0400. Each finalized invoice takes the next number of its circle in the same step that locks it, so two people finalizing at once still get two different numbers and no gap.

Typical setups:

- one circle for invoices and one for credit notes,
- a new circle per year with the year in the prefix,
- a separate circle for quotes.

Create or edit circles under **Settings → Billing**. A circle that has been used cannot be renumbered.