The short version: Most contractors should start with Helcim — no monthly fee, honest interchange-plus pricing, free invoicing, and a mobile reader for the job site. If you’re running $25k+/month through cards, Stax’s $99/month subscription beats everyone on price. If you just need to take a card today with zero setup, Square’s free reader is still the fastest on-ramp.
Contractors get the worst of both payment worlds: big tickets (where flat-rate percentages bleed you dry) and job-site mobility (where traditional countertop terminals are useless). The generic “best processors” lists don’t account for any of that. This one does.
Last updated: September 2026. Pricing verified against published rate cards and current reviews. See sources at the bottom.
Disclosure: Merchant Verdict is reader-supported. We may earn a commission if you sign up through links on this page — it doesn’t change our verdicts, and it never costs you extra. [AFFILIATE LINK: Helcim] [AFFILIATE LINK: Stax]
How we evaluated for contractors
We scored processors on the five things that actually matter to contracting businesses: (1) cost on large tickets ($1,000–$10,000 invoices, where a single percentage point is real money); (2) mobile/job-site acceptance; (3) invoicing and deposits; (4) ACH/bank-transfer options for big invoices; and (5) no junk fees or long contracts. Research is drawn from published 2026 pricing, NerdWallet, Business.com, and Merchant Maverick-style fee breakdowns — deep research, not hands-on testing, and we’ll show our math.
Our picks at a glance
| Processor | Best for | In-person rate | Online/invoiced rate | Monthly fee |
|---|---|---|---|---|
| Helcim | Most contractors | Interchange + 0.40% + 8¢ | Interchange + 0.50% + 25¢ | $0 |
| Stax | High-volume ($25k+/mo) | $0.08 + interchange (0% markup) | $0.15 + interchange (0% markup) | $99/mo |
| Square | Getting started / simplicity | 2.6% + 15¢ | 3.3% + 30¢ | $0 |
| Dharma | Values-driven shops | Interchange + 0.15% + 8¢ | Interchange + 0.20% + 11¢ | $20/mo |
| Stripe | Online-first (estimates → payment links) | 2.7% + 5¢ (Terminal) | 2.9% + 30¢ | $0 |
The $5,000 invoice test
This is the number that matters. A contractor collecting a $5,000 final payment by card — keyed or invoiced — pays wildly different amounts depending on the pricing model. Interchange (the wholesale cost) is identical everywhere since honest processors pass it through at cost, so what actually differs is the markup:
| Processor | Markup above interchange | Markup in dollars |
|---|---|---|
| Stax | $0.15 flat | $0.15 |
| Helcim | 0.50% + 25¢ | $25.25 |
| Dharma | 0.20% + 11¢ | $10.11 |
| Stripe | 2.9% + 30¢ (blended, includes interchange) | $145.30 total |
| Square | 3.3% + 30¢ (blended, includes interchange) | $165.30 total |
For interchange-plus processors, add ~2% interchange (~$100) to get the total. The takeaway: on large invoices, flat-rate processors (Square, Stripe) cost 5–10x more in markup than interchange-plus options. A contractor running $40k/month in card invoices pays roughly $1,000+/month extra on Square vs. Helcim. That’s $12,000 a year — a truck payment — for the privilege of a free card reader.
The move for big invoices: push clients toward ACH. Helcim charges 0.5% + 25¢ for ACH (capped at $6) — a $5,000 invoice costs $6, not $197. Stax includes ACH processing in its plans. Any processor relationship should include an ACH option; it’s the single biggest fee saver available to contractors.
Best overall for contractors: Helcim
Why it wins: Zero monthly fee, interchange-plus pricing with fully published rates, free invoicing, and a mobile card reader ($199) for the job site. No PCI fees, no cancellation fees, no contracts. For the typical contractor doing $10k–$40k/month in cards, it’s the cheapest honest option — and the honesty matters in an industry full of ISO reps with leased terminals and 3-year contracts.
The details that matter for contractors: – Invoice from the truck, get paid by text/email link — no extra charge – Next-business-day deposits at no extra cost – Tap to Pay on iPhone available (+10¢/transaction) — no reader needed in a pinch – Fee Saver surcharging program lets eligible businesses pass card costs to customers (check your state rules) – 0.40% add-on for recurring billing (relevant for maintenance contracts)
Watch out for: the $15 fee on lost chargebacks, and at very high volume ($25k+/month) Stax’s subscription model starts winning on pure price. [AFFILIATE LINK: Helcim]
Best for high-volume contractors: Stax
Why it wins: At $99/month with zero percentage markup, Stax is mathematically unbeatable once your card volume crosses roughly $25k/month in person. A busy HVAC or roofing outfit doing $60k/month in cards can save $3,000+/year over Helcim. Month-to-month, no early termination fee, no PCI fee, and it integrates with 90%+ of POS systems — plus free reprogramming of existing terminals.
Watch out for: the $99 is dead money under ~$8k–10k/month in volume (Stax’s own guidance); tier pricing above Growth requires a sales call; chargeback fees aren’t prominently disclosed — get them in writing. Also note: Stax runs on Worldpay’s backend, and some merchants report account holds. Not a dealbreaker, but know it going in. [AFFILIATE LINK: Stax]
Best for getting started: Square
Why it’s here: You can take a card payment 10 minutes from now. Free magstripe reader, free POS app, no monthly fee, no paperwork. For a new contractor who just needs to collect a deposit today, nothing beats the on-ramp.
The honest warning: Square’s flat rates (2.6% + 15¢ in-person, 3.3% + 30¢ online) are expensive at contractor ticket sizes, and Square is the most aggressive in the industry about account holds and freezes — there are years of contractor complaints about frozen funds mid-project. Fine for getting started; plan your exit to interchange-plus once you’re established.
Also worth knowing
Dharma Merchant Services — Interchange-plus at some of the lowest published markups in the industry (0.15% + 8¢ in person), $20/month including PCI compliance, and a certified B-Corp that donates half its net profits. A strong pick for contractors who care where their money goes. Flag: conflicting statements about a $49 closure fee — reconcile before signing.
Stripe — the best choice if your business is really an online funnel (instant online estimates → payment links). 2.9% + 30¢ is pricey per transaction, but the developer tools and payment-link flow are unmatched. Not a job-site solution.
Payment Depot (owned by Stax) — the “Costco of processing”: interchange-plus with 0.2%–1.95% markup, no monthly fee per NerdWallet’s 2026 review, no cancellation fees. Worth a quote if you like the Stax family but not the subscription.
Surcharging and cash discounts: the contractor’s secret weapon
Many states allow merchants to pass credit card costs to customers via surcharging (capped, with disclosure rules) or offer cash discounts. For contractors with 3% card costs on $10,000 jobs, this is a $300-per-job question. The rules vary by state and card brand — and they’re tightening, not loosening — so verify current legality for your state before implementing. Helcim’s Fee Saver and Stax/CardX’s surcharging tools handle the compliance mechanics (disclosures, receipts, network registration) if you go this route. Done right, it’s the difference between eating $15,000/year in fees and eating $0.
What to avoid
- Leased terminals and 3-year contracts. The classic ISO trap: a “free” terminal that costs $50/month for 48 months with an early termination fee. If a rep won’t put all fees in writing, walk.
- Tiered/qualified pricing. “Qualified / mid-qualified / non-qualified” rate buckets are designed to make the advertised rate meaningless. Interchange-plus or flat-rate only.
- PCI non-compliance fees. Some processors charge $20–30/month if you skip their PCI questionnaire. Helcim and Stax don’t play this game; many ISOs do. Ask explicitly.
The verdict
Just starting out? Square — take money today, switch within 6 months. The standard contractor ($10k–$40k/month in cards)? Helcim — the best blend of price, honesty, and contractor-friendly tools. [AFFILIATE LINK: Helcim] Running serious volume ($40k+/month)? Stax — the subscription pays for itself many times over. [AFFILIATE LINK: Stax] Sending a lot of $5,000+ invoices? Whatever processor you pick, turn on ACH. It’s the highest-ROI settings change in this entire guide.
Frequently asked questions
What’s the cheapest way for a contractor to accept credit cards? Interchange-plus pricing with no monthly fee (Helcim) for most; a subscription model (Stax) above ~$25k/month. And ACH for large invoices — always ACH for large invoices.
Can contractors add a surcharge for credit card payments? In most states, yes, with rules: surcharges are capped (typically at 3–4%), must be disclosed before payment, and debit cards generally can’t be surcharged. Rules change — verify your state’s current law and use a compliant surcharging tool rather than DIYing it.
Is Square bad for contractors? Not bad — expensive at scale and risky on holds. It’s the best starter processor and one of the priciest permanent ones. The typical arc is Square → Helcim → Stax as volume grows.
Should I lease a terminal from a sales rep? Almost never. Buy a reader outright ($59–$349 depending on needs) or use Tap to Pay on your phone. Leases are where the industry’s worst abuses live.
Do I need a separate merchant account, or is Square/Stripe fine? Aggregators (Square, Stripe) are faster to set up but can freeze funds with limited recourse. Dedicated merchant accounts (Helcim, Stax, Dharma) take longer to approve but give you a real account in your business’s name and a human to call. For a contractor with real cash flow at stake, the dedicated account is worth it.
Methodology & sources
Evaluated against contractor-specific criteria (large-ticket cost, mobile acceptance, invoicing, ACH, contract fairness) using published 2026 rate cards and third-party reviews. The $5,000-invoice math is our own calculation from published markups; interchange (~2%) is passed through at cost by interchange-plus processors and is therefore identical across them. “Best” reflects fit for stated use cases, not universal superiority.
Sources: – Helcim official pricing: https://www.helcim.com/pricing/ – Business.com — Helcim review 2026: https://www.business.com/reviews/helcim-credit-card-processing/ – Business News Daily — Stax Review 2026: https://businessnewsdaily.com/16593-stax-by-fattmerchant.html – NerdWallet — Square fees 2026: https://www.nerdwallet.com/business/software/learn/square-fees – NerdWallet — Stripe fees (Jul 2026): https://www.nerdwallet.com/business/software/learn/stripe-fees – NerdWallet — Payment Depot review 2026: https://www.nerdwallet.com/business/software/reviews/payment-depot – paymentpop.com — Dharma Merchant Services reviews (pricing/contract details): https://paymentpop.com/merchant-accounts/dharma-merchant-services-reviews/ – Dharma high-volume pricing: https://dharmamerchantservices.com/pricing/high-volume-pricing/ – Business.com — Small business credit card processing guide: https://www.business.com/articles/small-business-credit-card-processing/ – Website Planet — credit card processing guide (contractor notes): https://www.websiteplanet.com/nb/credit-card-processing/