Cleaning up your customer list

Start with duplicates

This is the biggest category and the easiest win. Duplicates happen because someone typed "Jansen Ltd" when "Jansen Limited" was already there, or because the same customer came in through two routes.

Sort your company list by name and go through it once. The duplicates sit next to each other and you'll find them in half an hour.

Merge rather than delete: the history of both has to end up in one place. If your system can't merge, move the notes across by hand before you delete one — otherwise you lose exactly the thing that mattered.

Then the people

Contacts go out of date faster than companies. People change jobs, and at a company you haven't spoken to for a year there's a fair chance your contact has moved on.

You don't have to go and find out. Flag what you're unsure about and check it the next time you're ringing anyway. One question — *"are you still looking after this?"* — does it.

What you do deal with straight away: a contact you know has left gets deleted or marked inactive. A name that no longer works there but is still on your list is the reason someone eventually sends a quote to the wrong person.

What you may no longer keep

This is the side most people don't think about. Under UK GDPR you keep personal data no longer than you need it for the purpose. There's no number in the legislation; you set a period yourself and explain why it's reasonable.

In concrete terms: a prospect who said no three years ago and whom you've had no contact with since no longer has a purpose. Nor, usually, does the record of a customer who left five years ago.

The two periods that pull in opposite directions

This is where it gets confusing, because two rules apply at once and they point different ways. UK GDPR sets a maximum — don't keep it longer than you need it. HMRC sets a minimum — keep your business records at least this long, whatever anyone asks.

And the HMRC minimum depends on what kind of business you are. If you're self-employed, you must keep your records for at least five years after the 31 January submission deadline of the relevant tax year. If you run a limited company, it's six years from the end of the company financial year the records relate to — longer if a return was filed late, if a compliance check is open, or if the records cover something that spans more than one accounting period.

The practical consequence is the same either way: two regimes side by side. Your invoices, contracts and accounts stay for the HMRC period because they have to. Your conversation notes about a prospect who never became a customer go sooner, because there's no longer a reason to hold them.

Which means your system has to be able to delete a customer record without taking the invoices with it. If it can't, that's a real problem rather than a theoretical one. More in the piece on customer data and UK GDPR.

The notes you're better off removing

While you're tidying, go through your notes fields as well. There's often something in there that shouldn't be: a judgement about a person, a note about someone's health or personal circumstances, or speculation you'd never say out loud.

The test: would you say it if the customer were reading over your shoulder? They have the right to ask for a copy of what you hold about them, and you'd have a month to produce it — so that chance is real.

A two-hour tidy-up

Do it in this order and you'll be finished in an afternoon:

1. Sort by name and merge the duplicates.
2. Flag companies you've had nothing to do with for more than two years.
3. Delete or deactivate contacts you know have left.
4. Go through the notes on those old records and take out what shouldn't be there.
5. Decide a retention period, write it down, and clear out what falls outside it — checking the HMRC minimum for your legal form first.

And then never again

An annual big clean-out means you work with a dirty list for eleven months. Better that it stays clean by itself, and one habit is enough for that: update the record at the moment you're speaking to someone.

Then you correct a wrong phone number the moment you notice it, rather than making a note to do it later. Later doesn't happen, and in a year's time you'll be sorting for two hours again.