ACH (Automated Clearing House) moves money directly from one bank account to another. It's slow (1–3 business days) compared to card processing (instant authorization, next-day funding), but it's also dramatically cheaper. Most processors charge $0.25–$1.50 per ACH transaction — flat — versus 2.5%–3% on credit cards.
For any recurring billing over $50, B2B invoice over $200, or rent/membership/subscription model, ACH should replace credit card. A landlord collecting $2,000/month rent via card pays ~$60 in fees; via ACH, ~$1.
The trade-off is conversion: customers are more familiar with cards, and ACH requires bank routing and account number entry. Modern tools (Stripe ACH, Plaid, GoCardless) reduce this friction significantly.