Automate Invoice Chasing: Why UK Construction Firms Get Paid Late

Before you automate invoice chasing, a UK construction firm has to separate three things that all look identical on an aged debtor report: invoices that are genuinely late, invoices that were never properly due because a notice or a valuation is missing, and money contractually held back as retention. Only the first category should ever be chased automatically — chasing the other two costs you credibility with the customer and tells you nothing about your cash position.

That distinction is why generic credit-control software underperforms in construction. It reads a due date off an invoice and starts sending. In construction the due date is frequently the wrong question.

Why do UK construction firms get paid late?

Construction payment moves through a chain. A subcontractor applies for payment, the main contractor values the work, a payment notice is issued, and a final date for payment follows. Every link adds a step where the paperwork can fail, and each failure looks like a late payment from the bottom of the chain.

The scale is measurable, but only for the large payers. Under the Reporting on Payment Practices and Performance Regulations 2017, businesses exceeding two of three thresholds — turnover over £54m, balance sheet over £27m, more than 250 employees — must publish their payment performance twice a year. Analysis of that data reported by Construction News on 14 July 2026 put the construction median at 33 days against an all-sector median of 32, with 14% of invoices issued to large construction businesses paid after agreed terms during 2025 (Construction News, 14 July 2026; underlying returns at check-payment-practices.service.gov.uk, both checked 14 August 2026).

Read that honestly: the published data covers only large businesses, which is precisely the population that owes money to small building firms. It says nothing about what a small firm's own customers do, and it is a median, not your ledger.

A five-step diagnostic before you automate anything

Run this sequence over your last three months of overdue invoices before buying or building anything. It takes an afternoon and it usually changes what you decide to automate.

1. Split the ledger into three buckets. Genuinely overdue; not properly due (missing valuation, missing payment notice, disputed variation); and retention held under the contract. Count the value in each. If bucket two is the largest, an automated chaser will make things worse, not better — the fix is upstream in your application process.
2. Find the median gap between "work done" and "invoice raised". Not invoice to payment — work to invoice. In small building firms this is regularly the single largest delay in the cycle, and it is entirely within your control. No amount of chasing recovers a fortnight lost before the invoice existed.
3. Check whether each overdue invoice has an evidence trail. Signed variation, dated site instruction, agreed valuation, delivery note. Chasing an invoice you cannot evidence invites a dispute you will lose. Automation should surface which invoices lack evidence, not chase them harder.
4. Identify concentration. Work out what share of your overdue value sits with your top two customers. If it is most of it, you do not have a chasing problem; you have a customer-concentration problem, and the correct intervention is a conversation, not a sequence of emails.
5. Time the retention. List every contract with retention outstanding, the release trigger for each, and the date it should have been released. Retention money is not late until its trigger has passed — but a great deal of it quietly never gets asked for.

If, after this, bucket one is where the money is, automated chasing is worth building. If it is not, spend the money elsewhere.

Where to automate invoice chasing in UK construction, and where not to

The useful split is between the diary and the judgment.

Safe to automate: tracking due dates and final dates for payment per contract; watching for the payment notice that should have arrived; assembling the evidence pack for each invoice; sending pre-due-date and graduated overdue reminders on smaller accounts; logging every chase against the invoice; escalating to a named person when a threshold is crossed; producing the weekly list of retention releases now due.

Not safe to automate: the valuation itself; deciding whether a variation is chargeable; deciding whether to charge statutory interest on a key account; anything sent to a main contractor you depend on for the next three jobs.

Two construction-specific mechanics break naive automations outright:

Retention. Money withheld against defects, released on a contractual trigger. An automation reading gross invoice value will chase sums that were never due yet. Retention needs its own record with its own release date, tracked separately from the invoice.

The Construction Industry Scheme (CIS). Under CIS, a contractor deducts tax from a subcontractor's payment and pays it to HMRC — 20% for registered subcontractors, 30% for unregistered, 0% for those holding gross payment status. The deduction applies to the labour element, not to materials. A payment that looks 20% short is very often correct, and chasing it reads as though you do not understand your own invoice. Note also that from 6 April 2026 CIS contractors must again submit monthly nil returns where no subcontractor payments were made (HMRC guidance summarised by TaxAssist, checked 14 August 2026) — a compliance change, not a chasing one, but it lands in the same workflow.

This is the sort of scoping work an AI Opportunity Audit exists to do, and it is the same reasoning we apply to any process automation build: automate the parts that are the same every time, leave the judgment with the person who carries the relationship.

What the law lets you chase, and when

Two statutes matter and they do different jobs.

The Housing Grants, Construction and Regeneration Act 1996 governs when payment becomes due under a construction contract. The payer must issue a payment notice within five days of the due date, even where nothing is due. If the payer intends to pay less than the notified sum, a pay less notice is required — and where the contract is silent, the Scheme for Construction Contracts sets that at seven days before the final date for payment. Where neither notice is validly served, the notified sum generally becomes payable (Designing Buildings on pay less notices, checked 14 August 2026). A tracker that watches for a missing notice is worth more than a tracker that counts days overdue.

The Late Payment of Commercial Debts (Interest) Act 1998 gives an implied right to statutory interest at 8% above the Bank of England base rate on qualifying business-to-business debts, plus fixed compensation:

The reference rate is fixed twice a year rather than tracking the base rate daily: the rate in force on 30 June applies to debts falling overdue between 1 July and 31 December, and the rate on 31 December applies to the first half of the following year. Bank Rate was maintained at 3.75% at the Monetary Policy Committee meeting ending 17 June 2026 — the last decision before the 30 June fixing (Bank of England, June 2026 Monetary Policy Summary, checked 14 August 2026) — which puts the statutory rate for the second half of 2026 at 11.75%. Sources: Late Payment of Commercial Debts (Interest) Act 1998 and the 1998 Rate of Interest Order, both checked 14 August 2026.

Whether to exercise that right is a commercial decision, not an automated one. Describing the obligation is as far as this article goes; the rest is for your own solicitor or accountant.

What is changing, and what has not changed yet

Two reforms are in motion and neither is law today.

The government published its response to the Late Payment Consultation: Time to Pay Up on 24 March 2026, proposing a ban on the deduction and withholding of retention under construction contracts — explicitly subject to further consultation before a final decision (Hansard, 24 March 2026; GOV.UK consultation outcome, both checked 14 August 2026).

Separately, the Commercial Payments Bill [HL] would void payment terms beyond 60 days in business-to-business contracts and close the loophole allowing parties to contract out of the statutory interest rate. As of this writing it has completed Lords committee stage and has all Commons stages ahead of it; commencement is not expected before 2027 (UK Parliament bill page, checked 14 August 2026).

Already in force: the Reporting on Payment Practices and Performance (Amendment) Regulations 2025 came into effect on 1 March 2025 and require qualifying large businesses to report on retention terms for financial years beginning on or after 1 April 2025 (legislation.gov.uk, checked 14 August 2026). That reporting is public, and it is a reasonable input to a credit check on a new main contractor.

The practical point for a small building firm: build the workflow so the retention record is separable. If retentions are banned in a few years' time, you want to switch that logic off, not rebuild the system.

Frequently asked questions

Why do UK construction firms get paid late more often than other sectors? Construction payment runs through a chain of main contractors and subcontractors, and each link adds a valuation, a notice period and a retention deduction. Government payment-practices data published in July 2026 put the construction median at 33 days against an all-sector median of 32, with 14% of invoices to large construction businesses paid after agreed terms in 2025.

Can invoice chasing be automated when payments involve retention and CIS? Yes, but only the tracking and the reminders. Retention releases and Construction Industry Scheme deductions change what is actually owed, so an automation that chases the gross invoice value will chase amounts that were never due. Automate the diary, the evidence trail and the escalation; keep the valuation itself with a human.

What interest can a UK building firm charge on an overdue commercial invoice? Under the Late Payment of Commercial Debts (Interest) Act 1998, statutory interest runs at 8% above the Bank of England base rate, plus fixed compensation of £40, £70 or £100 depending on the size of the debt. The reference rate is fixed twice a year. This is general information, not legal advice.

Is automated invoice chasing risky if you depend on one main contractor? It can be, if the automation escalates on a fixed clock without anyone reading the room. The usual fix is to route anything owed by a key account to a person before it sends, and let the automation run unattended only on smaller or one-off customers where a firm reminder carries no relationship cost.

How much does it cost to automate invoice chasing for a small building firm? Ihsan Ops starts every engagement with an AI Opportunity Audit from £1,000, which is how the work gets scoped. A single well-scoped workflow build then runs £2,000–£5,000 and typically takes 2–4 weeks, with platform and model costs of roughly £100–£600 per workflow per month at production volume.

Where to start

Run the five-step diagnostic first. If most of your overdue value turns out to sit in bucket two — not properly due — fix the application and notice process before you automate a single reminder, because chasing invoices that were never due is how a building firm loses a main contractor.

If you want a second pair of eyes on which part of that cycle is actually costing you money, Ihsan Ops is a UK AI automation agency based in Bedford, and the first conversation is free: book a 30-minute discovery call.