Managing Credit Notes and “We Deducted £X” Underpayments: How to Close the Gap Quickly

Underpayments are sneaky. They look like a partial win because money has landed in the bank, but the gap sits there quietly, ageing, muddying your ledger and draining time. One week it is £150 “deducted for damage”. Next month it is £1,250 “pricing adjustment”. Then the customer decides every invoice is negotiable.

If you are seeing a steady drip of short pays, you are not alone. Late and delayed payments are still a major UK issue. Government consultation material states late payments cost the UK economy almost £11 billion per year and are linked to 38 UK businesses closing every day. DBT’s late payments infographic also highlights the time drain: affected businesses spend an average of 86 hours per year chasing late payments.

The point is simple: you cannot afford to let underpayments linger. You need a fast, repeatable process that closes the gap without turning every case into a long email chain.

This article shows you exactly how to do that.

Why “we deducted £X” happens so often

Most underpayments fall into 5 buckets:

1. They raised a dispute late and paid what they felt like
2. Their internal system applied an unauthorised credit note
3. They netted your invoice against a separate issue (set-off)
4. They used “proof” that does not match the contract (missing POD, missing timesheet, missing acceptance email)
5. They are testing you to see if you will chase

From a collections point of view, bucket 5 is the most dangerous. If you do not challenge the first short pay quickly, you teach them that deductions are allowed.

If you want a clear view of how set-off and counterclaims show up in real B2B recovery, read this first.

Your goal: stop arguing and start closing

When a customer underpays, the most common mistake is treating it like a normal overdue invoice and sending generic reminders.

You need to treat it like a mini dispute with one clear objective:

Get written confirmation of why they deducted, validate it against the contract, then close the gap with either:

• payment of the balance, or
• an agreed credit note, issued correctly, with a clear settlement timeline

Step 1: Lock down the basics in 10 minutes

Before you send anything, pull these items together:

• Original invoice, due date, payment terms
• Amount received and date received
• The short-paid amount and exact deduction reason (if they provided one)
• Remittance advice or payment reference (ask for it if you do not have it)
• The contract or PO clause they are relying on

Do not start debating until you have the remittance advice. Most underpayment chaos is because you are trying to guess their logic.

Step 2: Get the reason in writing, with evidence, and a deadline

A fast, practical message works better than a long one:

• confirm you received £X
• confirm there is a short payment of £Y
• ask for the remittance advice and the deduction rationale
• set a deadline (48 hours is reasonable)
• state that undisputed sums remain payable and the balance will be chased

If you need a clean template approach, Taurus covers how to structure collection letters here.

Step 3: Classify the deduction so you pick the right response

Not all deductions are equal. Classify it immediately:

Type A: Legit admin errors (fast win)

Examples:

• duplicate payment assumption
• wrong supplier account
• VAT mismatch
• portal coding issue
• they applied an old credit note

Action:

• provide a statement, invoice copy, and request payment of the balance on the next payment run

Type B: Contract or pricing disputes (needs contract alignment)

Examples:

• “rate should be £X per unit”
• “you billed the wrong lane”
• “discount applies”

Action:

• ask for the PO, rate card, or email approval that supports their claim
• compare against your contract and quote
• if you agree, issue a credit note properly (see Step 6)
• if you do not agree, demand the balance and treat the deduction as unauthorised

Type C: Service issues (partly legitimate, often weaponised)

Examples:

• “late delivery”
• “damage”
• “SLA breach”
• “missing POD or timesheet”

Action:

• request evidence and a formal dispute notice
• confirm they cannot withhold undisputed amounts
• move it through a dispute process with firm dates

Type D: Set-off and counterclaims (high risk if you allow it)

Examples:

• “we deducted because you owe us for another issue”
• “we are netting this against our claim”

Action:

• do not accept casual set-off unless your contract allows it
• separate undisputed from disputed
• insist on payment of the undisputed balance

Again, this is a common pattern and Taurus Collections explains it in practical terms here.

Step 4: Use a 3-line evidence test to decide if a credit note is valid

Before you agree to issue a credit note, run this quick test:

1. Is the deduction authorised by the contract or PO?
2. Did they notify you within the agreed dispute window (or a reasonable time)?
3. Do they have evidence that matches the clause they are relying on?

If the answer is “no” to any of these, you should not casually approve a credit note. Otherwise, you build a culture of deductions.

If you are dealing with contested debts, Taurus has a dedicated service page for handling disputes properly.

Step 5: Close the gap with a clear, time-bound settlement plan

Once you have validated the issue, you need to finish it. Not “continue the conversation”.

Use one of these 3 closures:

Closure option 1: Pay the balance now

Best for: admin errors and unauthorised deductions
You confirm the balance and request payment by a specific date or payment run.

Closure option 2: Issue a credit note and get the net paid immediately

Best for: genuine pricing mistakes
You issue a credit note with a reference to the invoice, then confirm the remaining balance must be paid within 7 days.

Closure option 3: Split settlement: pay undisputed now, park disputed with a deadline

Best for: service disputes
You demand payment of the undisputed amount immediately and agree a short window (for example 7–14 days) to resolve the disputed element.

This is where a structured dispute workflow stops cases dragging for months.

Step 6: Issue credit notes correctly so they do not create new problems

A sloppy credit note causes two issues:

• the customer keeps deducting because “credits are confusing”
• your ledger becomes impossible to reconcile

Your credit note should always include:

• the original invoice number and date
• the specific line items credited
• the reason code (pricing, return, SLA credit, damage claim)
• the approval reference (email or portal ticket ID)
• VAT treatment (consistent with the invoice)
• a clear instruction: “do not apply against unrelated invoices”

Then, send a revised statement immediately.

If you want to tighten this process across your whole ledger, it can be easier to outsource credit control so your follow-up and reconciliation is consistent.

Step 7: Add lawful pressure when the short pay is just stalling

If the customer is using deductions as a delay tactic, you need escalation tools.

Statutory recovery costs for late B2B payment

In many B2B situations, you can charge fixed recovery costs on late commercial payments:

• £40 for debts up to £999.99
• £70 for £1,000 to £9,999.99
• £100 for £10,000 or more

This can be applied per late invoice (subject to the rules). It changes the tone because delay now has a clear cost.

Taurus also provides practical routes to quantify and communicate pressure:

• Late payment calculator.
• Late payment demands.
• Reclaiming costs and interest.

Follow the right pre-action steps if it is heading legal

If the short pay becomes a hard dispute and you may need court action, do it properly.

Step 8: Prevent repeat underpayments with 5 simple controls

If you keep seeing “we deducted £X”, prevention is usually cheaper than recovery.

1. Put dispute time limits in your terms (and enforce them)
2. Require deductions to be pre-approved in writing
3. Send statements monthly, not just invoices
4. Tie deliverables to evidence (PODs, timesheets, acceptance emails)
5. Escalate the first short pay quickly so it does not become a habit

Next steps

Underpayments and credit notes do not have to become a permanent leak in your cash flow. If customers are short-paying invoices, applying unauthorised credits, or hiding behind set-off tactics, you need a tighter process and faster escalation.

If you want help closing the gap quickly and professionally, Taurus Collections can support you through:

• • Debt recovery

• Outsourced credit control

• Dispute handling

You did the work and issued the invoice. Now make sure the full amount lands in your account, not just “most of it”.