"Payment reminder software" covers two very different problems in the UK market, and buyers often end up on the wrong product for their use case. One group is chasing unpaid invoices on 30-day terms from B2B clients. The other is recovering failed recurring subscription payments on Stripe. The tools look similar on the landing page. They're not the same.
This guide sorts the two categories, compares the leading tools in each, and explains why SMS matters for both (and why it lifts recovery rates by 30 to 40% when layered on email).
The two categories, clearly
Category 1: B2B accounts receivable (Chaser, Satago, InvoiceSherpa)
You invoice clients on 30, 60, or 90-day terms. They pay late. You need to chase them politely, then firmly, then with a credit control team on speaker phone. The tool automates the "politely to firmly" part of that flow.
This is a UK-heavy category because UK B2B still runs heavily on BACS and Direct Debit rather than card-on-file, which means late invoices are structural, not accidental.
Category 2: SaaS subscription dunning (Rekko, Churnkey, Stunning, Churn Buster)
You have customers on recurring subscriptions. Their card fails (expired, insufficient funds, bank declined). You need to recover the payment before they churn. The tool runs automated email and SMS sequences tied to Stripe webhooks.
This category is recurring-revenue-specific. You're not chasing someone who never paid, you're recovering from someone whose automatic payment broke.
Pick the wrong category and you waste money. A B2B AR tool can't see Stripe subscription events. A SaaS dunning tool can't track 60-day BACS invoices. Know which problem you have before comparing features.
Category 1: B2B accounts receivable software (UK)
| Tool | Best for | SMS | Pricing | |
|---|---|---|---|---|
| Chaser | UK SMBs, Xero/QuickBooks users | Yes | Yes (add-on) | From £35/mo |
| Satago | UK SMEs, invoice finance users | Yes | Limited | From £30/mo |
| InvoiceSherpa | QuickBooks/Xero users | Yes | Via Twilio | From $49/mo |
Chaser
Chaser is UK-born and UK-focused. Integrates deeply with Xero, QuickBooks, and Sage. Handles multi-stage reminder sequences with polite-to-firm escalation, credit control tasks, and a debt collection handoff at the end.
Best for. UK B2B companies with 20 to 500 open invoices at a time who need automated AR chasing.
Not for. SaaS recurring subscriptions. Chaser doesn't plug into Stripe subscription events.
Satago
Satago is UK-focused, combining credit control automation with invoice finance. Good for UK teams that want both chasing automation and access to short-term finance against outstanding invoices.
Best for. UK SMEs juggling cash flow on long payment terms.
Not for. Subscription dunning.
InvoiceSherpa
US-born but widely used in the UK QuickBooks and Xero ecosystem. Solid automation, Twilio-based SMS.
Best for. Accounting software users who want reminders automated without custom work.
Not for. Stripe subscription recovery.
Category 2: SaaS subscription dunning (UK-friendly)
| Tool | Best for | SMS | Pricing | |
|---|---|---|---|---|
| Rekko | Stripe SaaS $10K-£500K MRR | Yes | Yes (native) | From $29/mo |
| Churnkey | Mid-market, retention suite | Yes | No | Custom, MRR-scaled |
| Churn Buster | SMB to mid-market | Yes | No | MRR-tiered |
| Stunning | Bootstrapped, email-only | Yes | No | From $50/mo |
Rekko
Rekko is a Stripe-first dunning tool built for subscription SaaS. Five-minute OAuth setup, real-time webhook detection, and (unusually at this price) email plus SMS in the same sequence.
Best for. UK SaaS teams on Stripe that want to recover failed recurring payments without paying enterprise rates. Native UK GDPR handling, supports branded UK SMS sender IDs.
Not for. Chasing one-off B2B invoices on 30-day terms.
See the pricing page and Rekko vs Stripe Billing.
Churnkey
Full retention suite covering both failed payment recovery and cancel flow deflection. Good for mid-market SaaS that wants one tool for both.
Best for. Above £500K MRR, where cancel flow value is material.
Not for. Small teams that just need dunning to work.
More at Rekko vs Churnkey.
Churn Buster
Established email-only dunning tool. Solid deliverability, decent templates.
Best for. UK SaaS teams that want email-only recovery from a proven vendor.
Not for. Teams that want SMS.
See Churn Buster alternatives.
Stunning
Simple, email-only, Stripe-native dunning tool that's been around since 2015.
Best for. Bootstrapped teams under £50K MRR that want the cheapest email-only option.
Why SMS matters for both categories
Whether you're chasing a £8,000 B2B invoice or a £49 failed subscription, SMS consistently lifts response rates by 30 to 40% over email alone. The reason is structural:
- Open rates. Email opens average 20 to 30% in dunning and chasing contexts. SMS opens average 90%+ within three minutes.
- Response time. Email replies average hours to days. SMS replies average minutes.
- Channel trust. UK consumers and decision-makers increasingly treat SMS as the legitimate financial channel because banks, HMRC, and payment providers all use it.
For B2B AR, SMS is often used for the "escalation" stages when email has been ignored. For SaaS dunning, SMS is used alongside email from the first sequence step to maximize recovery speed before the customer cancels or the card hard-fails.
If your chosen tool is email-only, you're structurally capping recovery performance at the email ceiling. That's fine for very small operations. It's not fine once recovery is worth meaningful money.
UK compliance notes for SMS reminders
A few specifics for UK teams sending payment reminder SMS:
- PECR. Transactional messages (like a dunning message about a failed payment) fall into the "legitimate interest" category and don't require explicit opt-in. You still need to honor STOP replies immediately.
- Branded sender ID. The UK allows alphanumeric sender IDs (e.g., "Rekko", "YourBrand"). This lifts open rates because recipients see your brand name. Worth using if your tool supports it.
- Timing windows. Send between 8am and 8pm UK time. Most tools allow configurable send windows.
- Frequency caps. Don't bombard. 2 to 3 SMS messages over a 10-day recovery sequence is reasonable. More than that and you're risking complaints.
How to pick between the two categories
Ask yourself one question. "Is the payment I'm trying to recover a failed recurring subscription, or an unpaid one-off invoice?"
- Failed recurring subscription on Stripe. You need a dunning tool. Look at Rekko, Churnkey, Churn Buster, Stunning.
- Unpaid one-off invoice on 30-day terms. You need a B2B AR tool. Look at Chaser, Satago, InvoiceSherpa.
- Both. You need both tools. They're cheap enough that running both is fine, and they solve genuinely different problems.
Honest recommendation for UK teams
If you're a UK SaaS founder with Stripe subscriptions and your main problem is failed card payments, Rekko is the fit. Five-minute setup, email plus SMS, flat pricing, clean UK GDPR handling, branded UK SMS sender IDs.
If you're a UK services business invoicing clients on 30-day terms, Chaser is the natural pick. UK-born, UK-focused, integrates with the accounting tools UK SMBs actually use.
If you're doing both (a SaaS with a services arm, or a consultancy with a retainer product), run both tools. They're additive, not overlapping.
Try Rekko free
For Stripe SaaS teams in the UK that want subscription recovery with both email and SMS, Rekko takes about five minutes to set up. Connect Stripe, pick a sequence, start recovering.
- Flat pricing from $29/month
- Email plus SMS in one sequence
- Branded UK SMS sender IDs
- UK GDPR compliant opt-out handling
- Real-time Stripe webhook detection
Start your 14-day free trial. No credit card required.