Invoice Ninja
Forever-free invoicing for up to 5 clients: recurring invoices, online card payments, a client portal, time tracking and expenses.
Paddle
No special deal right now, just standard fees: 5% + 50¢ per transaction, no monthly fee. Merchant of record for software and SaaS, with global sales tax handled.
Stripe
No special deal right now, just standard pay-as-you-go fees: online payments and subscriptions with no setup or monthly fees. UK cards 1.5% + 20p.
Square
Free Square plan: take card payments in person, online and by invoice, with no monthly fee, just per-transaction rates.
Zoho Invoice
Free invoicing with multiple payment options, recurring invoices and payment reminders, for up to 2 users.
Tally
Unlimited forms and submissions free, including payments, signatures and file uploads.
Deftform
Unlimited forms and responses with Stripe payments and your own domain, for one payment.