Flux lets engineering firms take cards for convenience, ACH for larger invoices where the economics are friendlier, and pass the processing fee to the client at checkout where local rules allow.
Why engineering firms choose Flux
ACH for large invoices
Route retainers and big invoices over ACH where the per-transaction economics beat cards.
Pass the fee where allowed
On consumer pass-through, the processing fee is added to the client's total at checkout, where local surcharging rules allow.
Books that reconcile
A QuickBooks sync keeps engineering firms from retyping every payment into the accounting system at month end.
How engineering firms get paid
For engineering firms, ACH usually fits large invoices and retainers, cards suit smaller or on-the-spot payments, and Flux handles both through one integration with a clean record for your books.
A typical Flux setup for engineering firms
Engineering revenue is progress-billed: monthly invoices against a contract amount, time-and-materials billing on open-ended work, and task-order invoices on municipal and public contracts. ACH carries nearly all of it, settling in 1-3 business days, because the payers are businesses, agencies, and districts rather than consumers. A hosted payment link on each invoice gives a public-sector AP clerk a way to pay electronically without their IT department setting up a vendor portal integration.
Firms doing residential work, such as structural letters or septic designs, add card payment for homeowners, settling in 1-2 business days. Subconsultant costs flow through progress invoices as itemized lines. The REST API matters more here than in most industries: firms generate invoices inside project accounting systems and push them to Flux for collection, with QuickBooks sync closing the loop on the ledger side so billed and received never drift apart.
What engineering firms should watch
Public-sector clients pay reliably but slowly, on their own statutory schedule, and no payment tool changes that cycle. What you can control is invoice quality: progress invoices that match the contract's schedule of values, with correct task-order references, clear review without correction rounds, and every rejected invoice restarts the clock. For private clients, a payment link with net-30 terms shortens the only part of the cycle that is actually yours to shorten.
Retainage-style holdbacks and disputed change orders are where fees strand. Bill approved change orders immediately as separate line items rather than letting them accumulate into a contested final invoice. On small residential work, collect the fee before stamping and releasing the deliverable; a homeowner who already holds the sealed drawings has little reason to hurry. Card payment at delivery makes that gate practical without slowing the handoff by more than a day or two.
Simple, transparent pricing
Flux charges a flat 2.9% plus 30 cents per transaction, with volume discounts for higher-volume engineering firms and the option to pass the fee to the customer at checkout where local surcharging rules allow. No setup fees and no contracts. Accounts processing under $100,000 a year in card volume may be subject to a $20 monthly account fee.
Frequently asked questions
How do engineering firms accept payments with Flux?
Engineering Firms accept credit and debit cards, ACH bank transfers, and stablecoins through one Flux integration, with drop-in hosted fields that keep card data off your own systems.
What does Flux charge engineering firms?
A flat 2.9% plus 30 cents per transaction, with volume discounts for higher-volume merchants and no setup fees or contracts. Accounts processing under $100,000 a year in card volume may be subject to a $20 monthly account fee. You can also pass the processing fee to the customer at checkout where local surcharging rules allow.
How fast do engineering firms get their money?
Card payments settle in one to two business days and ACH in one to three business days. Stablecoin payments go to your wallet instantly.
Can a city or district AP department pay us through Flux?
Yes. The hosted payment link supports ACH, which is how most public-sector AP teams prefer to pay electronically. Payment links carry your invoice reference, which keeps their remittance matched to your receivable.
How do we handle progress billing against a contract amount?
Invoice monthly for the percentage complete, each with its own payment link, and bill approved change orders as separate items. The REST API can generate these from your project accounting so billing follows your earned-value numbers.
Should we take card payments for small residential jobs?
Yes. Collecting a card payment before releasing stamped documents closes the gap between delivery and payment on exactly the jobs where chasing an invoice costs more than the fee justifies. Cards settle in 1-2 business days.
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