"Aged-debtor diagnostic" has no formal accounting definition; people use it for a structured look at your aged receivables report that goes past the totals and asks why each overdue invoice is overdue: disputed, slow, stuck in the client's paperwork, or a failed direct debit. You can run one in about 20 minutes from Xero or QuickBooks, and what you get out of it is a short list of named actions, each with an owner and a date.
In this article
The short version
- The term has no formal accounting definition and usually means a structured review of your aged receivables that asks why each overdue invoice is overdue.
- Run the Aged Receivables Summary and Detail in Xero, or Accounts Receivable Ageing in QuickBooks, on the same day each month and keep last month's export.
- In about 20 minutes, clean the report, check concentration, tag each overdue invoice as disputed, slow, blocked or a failed collection, and compare with last month.
- Each cause needs its own response: fix and credit disputes, call slow payers, reissue blocked invoices with the PO, and retry failed collections within days.
- Escalate if one client tops the concentration check two months running, an undisputed balance passes 90 days or a dispute sits for a month with no owner.
What you need before you start
In Xero, run the Aged Receivables Summary for the overview and the Aged Receivables Detail for invoice-level work. In QuickBooks, run Accounts Receivable Ageing Summary and Detail from Reports, and use the Min. Days Past Due filter to show only overdue invoices.
Run it on the same day each month, ideally the last day, and export both reports to a spreadsheet. Keep last month's export to hand, because the change from month to month often tells you more than the snapshot.
An MSP ledger suits this kind of review because it mixes invoice types that go overdue for different reasons. Managed services, per-seat licensing, projects, hardware and annual renewals all sit in one report, and a £2,000 overdue balance means something quite different depending on which it is.
The 20-minute review
Take a hypothetical MSP with about 50 clients and £96,000 on its aged receivables report at 30 September.
Minutes 0 to 3: clean the report. Allocate any payments sitting on account, apply open credit notes, and remove duplicates or voided invoices. This often clears a few "overdue" balances the client never owed.
Minutes 3 to 5: read the shape. £38,000 is overdue, about 40% of the ledger. Most of it is under 30 days, which on its own looks like ordinary slow payment. The £7,500 over 60 days gets a closer look.
Minutes 5 to 8: check concentration. Sort the Detail report by client. One managed services client paying by bank transfer holds £11,400, or 30% of everything overdue.
Minutes 8 to 15: tag every overdue invoice with a cause. Add one column and choose from four: disputed, slow but undisputed, blocked by the client's process, or failed collection. A glance at the email thread or ticket usually settles it. In the example, the £4,300 in 61-90 days is an annual backup renewal waiting on a purchase order, £2,400 over 90 days is a hardware invoice disputed over two returned laptops, and three direct debit clients have £3,900 between them that should never have been overdue.
Minutes 15 to 18: compare with last month. If the 31-60 bucket has grown while billing hasn't, invoices are rolling forward unpaid. If a client appears in the concentration check for the second month running, flag it.
Minutes 18 to 20: write the action list.
By the end, more than half the £38,000 has a specific cause that a general reminder won't fix. The remaining £16,000, spread across 23 clients, is routine slow payment.
What to do with each kind of overdue invoice
Each cause needs a different response, and chasing with the wrong one wastes time or strains the relationship.
| Cause | Typical MSP example | What to do |
|---|---|---|
| Disputed | Wrong seat count, a milestone not signed off, returned hardware | Stop chasing, fix the issue, issue a credit note and reissue the balance |
| Slow but undisputed | A large client who pays everyone late | A call from someone senior, a date confirmed in writing, and a pause on new project work if your terms allow |
| Blocked | Missing purchase order number, invoice not uploaded to a supplier portal | Get the PO, reissue, and record the requirement on the client so the next invoice goes out right |
| Failed collection | Insufficient funds, cancelled mandate, changed bank details | Retry or re-collect within days, confirm the mandate is live, and offer another way to pay if it's been cancelled |
Failed collections are the easiest to take off your list. Adfin retries a failed direct debit for free and can fall back to the client's card or send a payment link, so a failed collection gets another attempt without anyone touching it. For the slow payer holding 30% of your overdue balance, it may also be the moment to propose direct debit at renewal.
The action list and when to escalate
Each line names the client, the amount, the cause, the next step, the owner and the date. For the example ledger, that's five lines, and the biggest is a phone call.
Keep the list with the month's export and start next month's review by checking what happened to each line. After a few months you'll have a record of which clients dispute, which get blocked by paperwork and which just pay late, and you can set terms and payment methods on that basis.
Escalate to whoever owns the business or the finance function if you see:
- the same client in the concentration check two months running
- a balance over 90 days that isn't disputed
- more than one failed direct debit from the same client
- a dispute open for a month with no owner
The chasing that follows the review is the bigger, repeating job. Adfin's Customer Agents can handle the routine group, chasing each client over email, SMS or WhatsApp on a timing and channel suited to them, sending a statement when someone goes quiet and routing a seat-count query to the right person, all within rules you set and approve.
Common questions
Is an aged-debtor diagnostic a standard accounting term? No. No professional body defines it; people use it to mean a structured review of an aged receivables report that ends in a list of actions.
Which report do I use in Xero? The Aged Receivables Summary for the overview and the Aged Receivables Detail for invoice-level work.
Which report do I use in QuickBooks? Accounts Receivable Ageing Summary and Detail, under Reports, then Standard reports. The Min. Days Past Due filter shows only overdue invoices.
How often should an MSP review its aged debtors? Monthly, on the same day each month, with a quick weekly look at the largest overdue balances and open disputes if your ledger is growing fast.
Why would a direct debit client appear as overdue? Usually a failed collection, a cancelled mandate, changed bank details or a collection that was never raised. Check each one individually.
What should come out of the review? A short action list naming the client, amount, cause, next step, owner and date for every overdue balance that needs more than a routine reminder.
Sources
- Xero - Accounts receivable aging report guide (accurate as of September 2026) https://www.xero.com/us/guides/accounts-receivable-aging-report/
- Intuit QuickBooks - Run Accounts Receivable Ageing reports (UK) (accurate as of September 2026) https://quickbooks.intuit.com/learn-support/en-uk/help-article/accounts-receivable-reports/run-accounts-receivable-ageing-report/L4N7PC2hg_GB_en_GB
- Adfin - Next-generation direct debit (accurate as of September 2026) https://www.adfin.com/direct-debit-payments
- Adfin - Credit control (accurate as of September 2026) https://www.adfin.com/credit-control
