Debtor days (also called Days Sales Outstanding, or DSO) measures how long it takes your business to collect payment after an invoice is raised. The formula:
Debtor Days = (Trade Debtors ÷ Annual Revenue) × 365
A business with £200,000 in outstanding invoices and £1.5M annual revenue has debtor days of approximately 49. The UK SME average is around 56 days — meaning most businesses are waiting nearly two months to be paid. Industry benchmarks vary: professional services averages 45 days; construction averages 72 days.
Reducing debtor days by even 10 days on £1M annual revenue frees up approximately £27,000 in cash flow.
The single fastest way to reduce debtor days is to eliminate the gap between delivery and invoicing. Many SMEs batch invoices weekly or monthly — adding 5–15 days to DSO before the payment clock even starts. Automatic invoice generation from your accounting platform (Xero, FreeAgent, QuickBooks) the same day work is completed can meaningfully shorten DSO without any collections activity.
Implementation: Set automatic invoice generation triggers in your accounting platform based on project completion or delivery confirmation.
UK businesses default to 30-day terms — often without asking customers whether shorter terms are acceptable. Many customers, particularly larger companies, will accept 14-day terms if asked upfront, especially for SME suppliers they want to support.
From 1 January 2024, UK businesses with over 250 employees must publish their payment practices data. Use this data (available at gov.uk) to identify which of your large customers are genuinely slow-paying before extending terms.
Implementation: Test shorter terms (14 or 21 days) on new customers. Review existing contracts at renewal. For customers where short terms aren't accepted, negotiate faster payment in exchange for an early payment discount.
Most businesses wait until an invoice is overdue before chasing. A reminder sent 3–5 days before the due date — confirming the invoice, the amount, and the payment method — catches admin errors before they become overdue balances and sets a professional expectation that payment is tracked.
Businesses using pre-due-date reminders typically reduce their overdue invoice rate by 15–20% with no additional collections effort.
Implementation: Set up automated pre-due reminders in your AR platform. Personalise with the invoice number, amount, and a payment link.
Email response rates for payment chasing average around 20–30%. Adding SMS raises that to 35–50%. Adding WhatsApp — where messages have 98% open rates — is increasingly common for UK businesses chasing SME and consumer debtors.
The optimal outreach sequence varies by debtor type: email-first for corporate customers, WhatsApp or SMS for SME and trade customers. AR platforms like Equisettle automate multi-channel sequences so each invoice follows the right outreach pattern automatically.
Implementation: Segment your debtor book by customer type and configure channel preferences. Use automated AR software to manage multi-channel sequences without manual effort.
Invoice friction adds days to DSO. Customers who receive a PDF with a bank account number and sort code face more friction than those who receive a payment link. Businesses that add a "Pay Now" link to reminder emails — connecting to a payment portal where the customer can pay by card or bank transfer in two clicks — reduce DSO by an average of 12 days.
Implementation: Enable a payment portal through your AR platform or accounting software. Include the payment link in every reminder email and on every PDF invoice.
Customers who can't pay in full often don't tell you — they go silent. A proactive payment plan offer ("we can split this across three monthly instalments") turns a potential bad debt into a scheduled recovery. Research shows customers offered a structured plan are 3× more likely to pay in full than customers who face escalation.
Implementation: For invoices overdue more than 14 days with no response, trigger a payment plan offer via email or SMS. Set the plan terms to recover the full amount within 90 days.
The most impactful DSO reduction comes from identifying which invoices will go late — before they do. Machine learning models trained on payment history can predict with 94% accuracy which invoices will exceed their terms up to 14 weeks in advance.
This allows finance teams to prioritise proactive outreach on high-risk invoices while they're still current — rather than reacting after the due date has passed. Businesses using predictive AI collections report DSO reductions of 30–50%.
Implementation: Use an AR platform with built-in predictive AI, such as Equisettle. The model runs automatically across your portfolio and surfaces at-risk invoices daily.
Debtors learn your escalation patterns. If your practice is to send three reminder emails and then take no further action, customers who stretch payment will stretch to four weeks. A clear, consistent escalation path — reminder → phone call → formal notice → solicitor letter — that you genuinely follow signals that your payment expectations are firm.
For B2B invoices, UK businesses are entitled to claim UK statutory interest at Bank of England base rate plus 8% from the moment an invoice becomes overdue. Informing customers of this entitlement in your final reminder improves payment rates without requiring you to actually claim the interest.
Implementation: Document your escalation path. Automate the first three steps. Set a calendar trigger for step four (formal notice) rather than letting overdue invoices age indefinitely.
| Method | Typical DSO Reduction | Effort |
|---|---|---|
| Invoice on delivery (not monthly batch) | 5–15 days | Low — system change |
| Shorter payment terms | 7–14 days | Low — policy change |
| Pre-due-date reminders | 5–8 days | Low — automation |
| Multi-channel outreach (add SMS/WhatsApp) | 8–12 days | Medium — tool setup |
| Payment link in reminders | 8–12 days | Low — tool setup |
| Proactive payment plans | 3–7 days | Medium — process change |
| AI risk scoring (proactive outreach) | 15–25 days | Low — platform choice |
| Consistent escalation | 5–10 days | Medium — policy + discipline |
Most of the methods above can be automated with the right AR platform. Key features to look for:
Equisettle combines all six in a single platform from £49/month with a 48-hour setup and no credit card required for trial.
[Calculate how much cash flow you could unlock with a free Equisettle trial →]
