Payment downtime costs: lost sales, recovery and backup plans
Find out what an interruption would cost your business, then decide what it is worth spending to reduce the impact.
The short answer
Estimate downtime using sales that are genuinely lost, the contribution those sales would have earned and additional recovery costs. Separate this from takings merely delayed or paid another way. Compare realistic incidents and backup options; a supplier uptime percentage alone does not measure your checkout’s business impact.
In this guide
Identify what stopped and what was actually lost
A failed terminal, lost internet connection, payment-platform outage and broken EPOS integration can have different consequences. One may affect a single checkout; another may stop the whole site. Some customers may pay another way, wait or return later.
Record the start and finish, affected functions, trading conditions and practical workaround. Count sales not recovered, rather than treating every attempted payment during the incident as permanently lost revenue.
For a trading comparison, use the contribution remaining after costs that would have varied with those sales. Add extra engineering, overtime or recovery work where genuinely incurred. Normal wages or rent should not be added again if already in your baseline.
Worked example: two hours without normal payments
Fictional incident. During two hours, 30 customers per hour would normally spend £20 each. That is £1,200 of sales exposed. Assume 40% are recovered through another method or later purchase; 60%, or £720, are lost.
At an assumed 40% contribution margin after variable costs, lost contribution is £288. Add £80 of extra recovery spending and the modelled business impact is £368.
Do not add the £720 lost revenue on top of the £288 contribution: the contribution calculation already reflects the sales impact on the stated basis. Record unpriced reputation or customer-service effects separately.
Repeat the calculation for a busy service, an ordinary period and a quiet period. Use actual incident records where possible, and show the uncertainty when estimating customer behaviour.
Ask what an uptime promise measures
A 99.99% availability figure, applied to every minute of a 365-day year with no exclusions, corresponds mathematically to about 52.6 minutes of downtime. That calculation does not establish what a particular supplier promises, when an incident happens or whether your hardware, broadband and integrations are covered.
Ask for the measurement period, service boundary, maintenance exclusions, reporting method and remedy. Distinguish a target, historical result and contractual commitment. A central platform can be available while a local till cannot trade.
Do not turn a quoted uptime number directly into a guaranteed annual savings figure. You need evidence of the types of interruption the proposal actually prevents.
Match the backup to the failure
| Failure | Option to investigate |
|---|---|
| One terminal stops | A provisioned spare, another working terminal or an approved alternative acceptance method. |
| Local internet fails | Tested mobile or alternative connectivity with the required devices configured. |
| Payment service fails | Provider-approved offline facilities, where supported, or an independently assessed alternative. |
| Integration fails | An agreed standalone workflow and reconciliation procedure. |
| Power or site interruption | A wider continuity plan appropriate to the business, with safe operating limits. |
Square’s offline guidance illustrates why this matters: support differs by device and payment method, and the merchant carries specified later decline and dispute risks. Offline acceptance is not the same as a successful online authorisation.
Keep a short recovery plan and review incidents
Give staff an escalation contact, approved fallback and clear instructions for recording incomplete transactions. Avoid repeatedly charging a customer before establishing the status of an uncertain payment. Follow the payment provider’s process.
After recovery, reconcile pending payments, refunds, orders and stock. Record extra costs and what was recovered. Use those records to improve the next service or support decision.
The connectivity and support guides help price preventive measures. Keep downtime scenarios alongside the calculator report, rather than entering hypothetical lost sales as ordinary processing fees.
Common questions
Should I count all sales during an outage as lost?
No. Some may be delayed, recovered later or paid by another method. Estimate the genuinely lost contribution and separately incurred recovery costs.
Is 99.99% uptime enough to choose a provider?
No. Check what is measured, exclusions, actual trading impact and the rest of the checkout. The number alone does not establish end-to-end availability or value.
Bring your costs into one clear comparison.
Use the free calculator for your payment fees and supported fixed costs. Keep the wider operating budget alongside it, or ask for a free initial review of an unclear charge or quotation.
No registration required to use the calculator.
Sources and how to use this guide
Primary references checked on 15 October 2026:
- Ofcom: choosing business connectivity and service levels
- Square UK: offline payment support and risks
Worked examples are fictional planning scenarios, not provider quotations, market averages or customer results. They use the costs and assumptions stated, on a consistent VAT basis. Confirm current prices, eligibility and terms in writing.
Read the calculator method and limitations or about EPOS Savings. Source links do not imply a partnership or product endorsement.