Invoice Timing | Tabs Docs

The invoiceDateStrategy field controls when the invoice is issued relative to the billing period.

Invoice date strategies

First of period

FIRST_OF_PERIOD — Invoice generated on the first day of the billing period. Use for billing in advance.

Last of period

LAST_OF_PERIOD — Invoice generated on the last day of the billing period.

Arrears

ARREARS — Invoice generated on the first day after the billing period ends.

Advanced due start

ADVANCED_DUE_START — Invoice generated before the billing period starts, dated so the payment due date lands on the first day of the period: invoice date = period start − payment terms. Use when payment must clear before service begins.

January billing period — billed monthly

Strategy	Invoice issued
First of period	Jan 1
Last of period	Jan 31
Arrears	Feb 1
Advanced due start	Dec 17 (Jan 1 − 15 days)

When to use each

Subscription / flat fee, billed in advance

FIRST_OF_PERIOD

Subscription / flat fee, end of month

LAST_OF_PERIOD

Usage-based billing

ARREARS or LAST_OF_PERIOD

Milestone / delivery-based

ARREARS

Payment required before service starts

ADVANCED_DUE_START

Usage billing note: Unit and tiered products should almost always use ARREARS or LAST_OF_PERIOD. Using FIRST_OF_PERIOD on a usage-based product will invoice before any events have been reported.

Invoice date strategy Required: Controls when the invoice is generated relative to the billing period. Must be one of FIRST_OF_PERIOD, LAST_OF_PERIOD, ARREARS, or ADVANCED_DUE_START.