Processing fees are automatically applied based on the payment method used for an invoice. These fees can change depending on whether members pay partially, use multiple cards, or switch between card and non-card payments.
This article provides practical examples that show how processing fees behave under various conditions, helping you understand how Flex calculates, updates, and displays them in real billing situations.
Before you start
Processing fee configuration
In all use cases in this article, a member must pay $100. The operator has the following processing fee configuration:
Card Type | Fee Percentage |
Any card | 2% |
Visa | 3% |
Mastercard | 5% |
Debit card | 0% (only applicable with Stripe integration) |
Below are examples showing how the processing fees behave under different payment scenarios.
Use case 1 – Partial direct debit, then card payment
Default payment method: Direct Debit (Payment Method on the invoice is Stripe ACH, SEPA, GoCardless, or Ezidebit)
Initial estimated price: $100
The member pays $50 via Direct Debit.
Remaining balance: $50
The member then pays the remaining amount with Mastercard.
A processing fee of $2.50 is generated for the remaining $50, calculated as 5% of $50. The user is alerted about the processing fee.
The amount paid via Mastercard: $52.5.
Total paid: $102.5
Use case 2 – Card first, then non-card payment (no fee update)
Default payment method: Mastercard.
A processing fee exists in the invoice of 5% of the invoice total amount: $5
The member selects Visa as the payment method.
Processing fees updated to 3%, and the final price is recalculated to $103.
The member pays $50 via Visa.
Remaining balance: $53
The member pays the rest via Bank Transfer.
The processing fee remains intact (calculated at 3% and based on the entire invoice amount).
The amount paid via Visa: $50.
The amount paid via Bank transfer: $53.
Total paid: $103
Use case 3 – Multiple card payments (fee based on first card)
Default payment method: Mastercard.
A processing fee exists in the invoice of 5% of the invoice total amount: $5
The member pays $50 via Mastercard.
Remaining balance: $55
The member then pays the rest via Visa.
The processing fee remains intact (calculated at 5% and based on the entire invoice amount).
The amount paid via Mastercard: $50.
The amount paid via Visa: $55.
Total paid: $105
Use case 4 – Non-card payment, then card payment
Default payment method: Visa
Initial estimated price: $103 with a $3 processing fee
User chooses to pay $50 in cash.
The processing fee is removed, and the invoice amount resets to $100.
The amount paid via cash: $50.
Remaining amount: $50
The member then pays the rest with a Visa card.
A processing fee is added, and the invoice amount increases to $101.5.
The amount paid via cash: $50.
Processing fee generated: 3%*$50 = $1.5
Total payment via Visa: $51.50
Total paid: $101.50
Use case 5 – Card payment
Default payment method: Credit Card (Visa)
Base amount: $100
Processing fee applied: 3% → Final price = $103
The member pays $103 via Visa.
The fee is calculated based on the Visa rate (3%) and remains unchanged.
Total paid: $103
Use case 6 – Auto payment with multiple saved cards
The member profile has two cards saved:
Visa (3%)
Mastercard (5%)
Invoice Payment Method: Auto (no specific card selected)
The fee is automatically applied based on the first card on file (Visa) → 3% fee.
Total: $103
If the member manually switches to Mastercard later, the processing fee is recalculated based on the Mastercard rate (5%), and the new final price is $105.
Use case 7 – Direct debit and card saved
The member profile has both a Direct Debit bank account and a Visa card.
Default payment method: Auto
Since a direct debit method exists, the platform assumes the invoice will be paid via direct debit.
Result: No processing fee is generated.
Total: $100
Use Case 8 – Credit note allocated
Default payment method: Credit Card (Visa)
Base amount: $100
Processing fee applied: 3% → Final price = $103
A Credit Note of $50 is allocated to the invoice
The rest is paid with Visa
The processing fee is recalculated for the remaining $50 as 3% of $50, which equals $1.50.
The amount paid via Visa: $51.5.
Total paid: $51.5
Total allocated: $50