Every sales invoice copies its details from a customer record: the name it is addressed to, the email it goes to, the payment terms it states, the VAT treatment it applies. When those records are wrong, the errors repeat on every invoice. Invoices go to someone who left two years ago, a customer is set up twice and appears to owe half its balance on each account, and a business customer’s VAT number is missing just when you need it.
Signs your customer list needs cleaning
- Payments from one customer keep landing on the “wrong” account.
- The aged debtors report shows the same company under two or three spellings.
- Invoices bounce, or customers say they never received them.
- Credit control calls reach people who no longer deal with invoices.
- Hundreds of customers with no activity in years clutter every search.
A cleanup in six passes
Work through the list one problem at a time rather than one customer at a time. Export it to a spreadsheet first, so you can sort and filter.
1. Duplicates. Sort by name, postcode and email domain. “ABC Ltd”, “A.B.C. Limited” and “ABC (Leeds)” may be one customer or three. Where they are the same legal entity, merge them in the software if it supports merging, or move open items to the surviving record and deactivate the other. Keep the record with the longest history.
2. Legal name and company number. For limited companies, the invoice should show the customer’s registered name. Check it against the Companies House register and add the company number to the record. This matters most for credit control: you can only pursue the legal entity that contracted with you.
3. VAT numbers. For VAT-registered business customers, record their VAT number and check it is valid with HMRC’s online VAT number checker. Wrong VAT numbers cause problems when a customer reclaims VAT and when you need to show that a customer is in business.
4. Invoice contacts. Separate the person you sell to from the person who processes invoices. Add an accounts payable email where the customer has one, and remove personal addresses of people who have left.
5. Payment terms and credit limits. Make sure each record’s terms match what was actually agreed. Customers on “30 days” who have always been allowed 60 should be either corrected or formally moved to 60. Set credit limits for customers you sell to on account; see payment terms and credit policy.
6. Inactive customers. Deactivate customers with a zero balance and no sales for, say, 18 months. Do not delete them; you may need the history. Customers with old credit balances need investigating first: see old customer credit balances and supplier debit balances.
| Field | Why it matters | Source to check |
|---|---|---|
| Registered name | Invoice and legal claim are against the right entity | Companies House |
| Company number | Identifies the entity even if it changes name | Companies House |
| VAT number | Customer’s VAT reclaim; your evidence | HMRC VAT checker |
| Billing address | Required on a full VAT invoice | Customer’s confirmation |
| Invoice email | Invoices reach accounts payable | Customer |
| Payment terms | Due dates and credit control | Signed terms or order |
Setting up new customers
A clean list stays clean only if new customers are set up properly. Before the first invoice goes out:
- Collect the details in writing, ideally through a short form or your quote acceptance: legal name, company number, registered address, billing address if different, VAT number, purchase order requirements and invoice email.
- Check the company on Companies House: is it active, does the name match, are accounts overdue? A company with overdue accounts or a pending strike-off deserves a closer look before you give credit.
- Search your own customer list before creating a record, so you do not add a duplicate of a customer you already have.
- Agree payment terms and enter them on the record, rather than relying on a default.
- Ask about purchase orders. Many larger customers will not pay an invoice without a PO number on it; record whether one is required.
- Decide credit or prepayment. For new customers with no history, a deposit or payment in advance on the first order is reasonable.
Keep it clean
Assign one person to create and change customer records, and review a list of new and edited records each month. Run the duplicate check again every six months. A tidy customer list makes every other routine, from matching receipts to credit control, faster and more reliable.