Primary & Backup Payment Methods
Every Fluz account has a default funding source made up of two roles: a primary payment method and a backup payment method. Together they decide how a transaction is funded and what happens if the first attempt can't be completed.
| Role | Shown in app as | Must be a | Purpose |
|---|---|---|---|
| Primary | Preferred account | Bank account (ACH) | The default funding source charged first for transactions. |
| Backup | Backup card | Bank card (debit/credit/prepaid) | Charged if the primary funding source can't be charged. |
Each account has exactly one primary and one backup at a time. Selecting a new one replaces the previous selection for that role.
How It Works
When a user makes a purchase, funds a virtual card, or deposits to their Fluz balance, Fluz charges the primary funding source first — by default, the preferred bank account over ACH.
Because ACH payments can settle over several days or fail, a backup card acts as the safety net:
- When a user pays via ACH, a temporary hold may be placed on the backup card for the transaction amount.
- If the ACH payment clears, the hold is released within 1–7 business days.
- If the ACH payment does not clear, the backup card is charged instead.
A backup card must be on file before a transaction can complete.Fluz requires a valid bank card as the backup payment method so a transaction can still be completed if the primary funding source fails. Without one, transactions that depend on ACH cannot be started.
Configuring Primary & Backup
Primary and backup selection is managed in the Fluz app or web portal — not the API.The API can add, update, and delete the underlying bank cards, and link or remove bank accounts. However, choosing which funding source is the primary or backup is only available in the Fluz app or web portal.
On the web
- Open Accounts and Cards from the account menu (or go to
/accounts-and-cards). - In the Default funding source section at the top of the page:
- Select Manage preferred account to choose the bank account used as the default funding source.
- Select Manage backup card to choose the bank card charged if the preferred account can't be.
- Your selection is saved immediately.
On mobile
- Open the menu and tap Accounts and Cards.
- Under Default funding source, tap Manage preferred account or Manage backup card.
- Choose from your linked funding sources. Your selection is saved immediately.
If you don't yet have an eligible funding source, the app will prompt you to add one first — a bank account for the preferred account, or a bank card for the backup.
What Can Be Done via API vs. App / Web
| Task | API | App / Web |
|---|---|---|
| Add, update, or delete a bank card | ✓ | ✓ |
| Link or remove a bank account (Plaid) | ✓ | ✓ |
| Set which funding source is primary / backup | ✗ | ✓ |
See Bank Cards and Bank Accounts for the funding source operations that are available through the API.
Eligibility & Notes
- The primary payment method must be a linked bank account; the backup must be a bank card.
- Business accounts must complete KYB verification before funding sources — and therefore the default funding source — can be set.
- Some funding sources may be restricted for specific merchants or by account limits and won't be selectable as a default.
Want to learn more? Speak with our experts for more info or to request a demo.