---
agentTools:
  projectIndex: https://developer.bill.com/llms.txt
---

# Setting payment transaction numbers for personalized tracking

You can now set the `transactionNumber` field when you create a payment (`POST /v3/payments`) or bulk payment (`POST /v3/payments/bulk`).

You can set `transactionNumber` as a unique alphanumeric value for your system to track a payment transaction. The value must be 50 characters or fewer. If you do not set `transactionNumber`, BILL sets this field as a unique alphanumeric payment identification value.

See [/v3/payments](https://developer.bill.com/v3/reference/createpayment) in the API reference for more information.