Cleaning up your customer list

Start with duplicates

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

Do not search on the name — it is sometimes with Ltd, sometimes without, sometimes with the Irish spelling and sometimes without. Search on what is unique: phone number, email address, street plus number. Sorting by name and reading down the list once catches the obvious pairs in half an hour; the phone number catches the ones the name hides.

Merge rather than delete: the history of both has to end up in one place. Many systems have no merge button at all, and then this is handwork — copy the notes across before you delete one, or you lose exactly the thing that mattered.

Check three things on every merge: who owns the customer now, which open deals hang off which of the two records, and which price was agreed. Those are the three places where a merge does quiet damage.

Then the people

Companies stay, people move. Contacts go out of date faster than anything else on your list, and at a company you have not spoken to for a year there is a fair chance your contact has moved on.

You do not have to go and find out. Flag what you are unsure about and check it the next time you are 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 do not think about, and it is the side the Data Protection Commission cares about.

Under the GDPR, personal data may be kept only for as long as is necessary for the purpose it was collected for. The DPC calls this storage limitation, and its guidance adds the part people skip: in order to make sure data is not kept longer than necessary, you are expected to set time limits yourself for erasure or for a periodic review. There is no number in the Regulation. You pick the period, you write it down, and you must be able to explain why it is reasonable.

In concrete terms: a prospect who said no three years ago and whom you have had no contact with since no longer has a purpose. Nor, usually, does the sales note on a customer who left five years ago.

Six years, and a clock that starts later than you think

Now the part where a tidy-up can go wrong, because a second body of law points the other way — and in Ireland it points at one number.

Revenue is blunt about it on its own guidance for people starting and running a business: if you run a business you must keep certain records for tax purposes, and you must keep the original of these documents for six years. That holds whether you are a sole trader or a limited company; unlike some other countries, Ireland does not give the two a different period.

What counts is wider than invoices. Revenue calls the supporting paperwork linking documents — receipts for expenses, receipts for purchases, sales invoices, nominal ledgers and accounting books — and anything used to calculate your Income Tax, Corporation Tax or Capital Gains Tax falls inside it.

When the six years start is the part that catches people. Revenue’s own manual for its staff says records must generally be retained for six years from the date of the transaction, act or operation to which they relate — not from the end of the tax year, and not from the date you filed.

Three situations run longer, and two of them reach small businesses:

• You did not file a return. Then the period runs until six years after the end of the year in which the return should have been made — so failing to file extends the obligation instead of ending it.
• Something is already under inquiry, investigation, claim, assessment, appeal or proceedings. Then the relevant records stay until that matter is concluded, even if six years have passed. Revenue’s VAT guidance says the same thing in its own words: six years, or until the matter at issue is finalised.
• Property. Where a VAT-charged interest in property was acquired or developed before 1 July 2008, the records go six years after you dispose of that interest, and a waiver of exemption on a letting runs six years from the cancellation of the waiver.

And there is no shortcut: keeping anything for less than these periods needs written permission from Revenue. That is not a convention, it is on the page.

If you trade through a limited company, a second clock runs beside the first one, and it finishes later. Section 281 of the Companies Act 2014 requires a company to keep adequate accounting records, and section 285 requires those records to be preserved "for a period of at least 6 years after the end of the financial year containing the latest date to which the record, information or return relates".

Same number, different starting gun — and that is the whole practical difference. Take an invoice dated 3 March 2026 in a company whose financial year ends on 31 December. Revenue’s clock runs from the transaction, so it is up on 3 March 2032. Section 285 runs from the end of the financial year containing that date, so it is up on 31 December 2032. Nine months of difference, on the same piece of paper. If you are a company, use the later date and stop doing the arithmetic twice.

The two rules that look like they contradict each other

Read the two paragraphs above next to each other and it sounds like a trap. Data protection law says do not keep it longer than you need it. Tax law says keep it for six years. Which one wins?

Neither, because they are not actually fighting. A legal obligation to keep something IS a reason to keep it — it is the necessity, not an exception to it. The DPC says so itself on its guidance about the right to erasure: the right to be forgotten does not apply where processing is necessary for compliance with a legal obligation, or for the establishment, exercise or defence of legal claims.

So a deletion request does not reach your invoices while their six years are running. It does reach almost everything else.

The practical consequence is that your list has two buckets, and the work of a clean-up is mostly deciding which bucket each thing is in:

• Anything that supports a figure in a tax return — invoices, credit notes, receipts, the ledger — stays for the full period, because you are obliged to keep it. You may not use it for anything else in the meantime: the retention purpose is then the only purpose you have left, so no marketing, no analysis, no sales call built on it.
• Everything else — the sales notes on a prospect who never became a customer, the contact details of someone who left, the record of a quote that went nowhere — has no retention period at all and goes as soon as it has no purpose.

Which means your system has to be able to tell those two apart, and you have to be able to delete the second kind without disturbing the first. The grounds for all of this are set out in the piece on customer data and the GDPR.

One boundary worth knowing: the Data Protection Act 2018 is the Irish Act that sits alongside the Regulation, and it restricts the right to erasure further in specific cases (sections 43 and 60). Those restrictions are about public-interest objectives and freedom of expression, not about your sales notes — do not reach for them as a reason to keep something.

And deleting too early is an offence, not an inconvenience

This is the sentence that makes the six years real. Revenue’s own guide to self-assessment puts it plainly: "Failure to keep proper records or failure to keep them for the necessary six years, where you are chargeable to tax, is a Revenue offence. If you are convicted of a Revenue offence you could face a heavy fine and/or imprisonment."

In practice, the thing you are far more likely to meet is the administrative penalty rather than a courtroom: a person who fails to keep records or linking documents for a year of assessment or accounting period is liable to a penalty of €3,000, unless it is proved that nobody was chargeable to tax for that period.

For a limited company there is company law on top. Contravening the retention duty in section 285 is a category 2 offence under section 286 of the Companies Act 2014, which section 871 sets at a class A fine or up to twelve months on summary conviction, and a fine of up to €50,000 or up to five years on indictment. It becomes a category 1 offence — up to €500,000 or ten years — where the contravention persisted for three years or more, or where the company is later wound up unable to pay its debts and the failure contributed to that.

And it is not only the company that is on the hook: section 286(2) makes a director who fails to take all reasonable steps to secure compliance guilty of the same offence, with a defence only if he or she put a competent person in charge and actually monitored them.

None of that is a reason to keep everything forever. It is a reason to do the sorting properly once, rather than clearing out a folder because it looked old.

The notes you are better off removing

A pass of its own, and it is more uncomfortable than the duplicates, because it is your own sentences.

Go through the notes fields looking for two kinds of entry. Judgements about people — "difficult", "not a real decision-maker". And things noted in passing that do not belong there: an illness, a separation, someone’s money trouble.

The reason is not delicacy. Under the GDPR anyone can ask for a copy of the personal data you hold about them, and your notes are part of it. The DPC’s guidance for organisations is specific about the deadline: you must provide a copy without undue delay and in any event within one month of the request, and only extend that by two further months where the request is genuinely complex — and then you still have to say so inside the first month.

The test: would you say it if the customer were reading over your shoulder? "Rarely answers email, always picks up the phone" is useful and harmless. Most of the rest is neither.

These notes are also the easiest part of the whole clean-up, because they hang off no invoice and no return. Nothing in tax or company law requires them, so there is nothing standing in the way of deleting them.

A two-hour tidy-up

Not more. A data project is never finished; two hours finishes:

1. Thirty minutes on duplicates. By phone number and email address, not by name. Move the notes across before you delete the loser.
2. Twenty minutes on owners. Every customer gets a name beside it; a customer nobody owns is a customer nobody rings.
3. Twenty minutes on contacts. Delete or deactivate the ones you know have left, and flag the companies you have had nothing to do with for more than two years.
4. Thirty minutes sorting the two buckets. Which records support a figure in a return, and which are purely sales notes? The first group has six years to run; the second has none.
5. Twenty minutes deleting. Notes with no purpose go. Records whose six years have run out may go too — as long as no inquiry, claim or appeal is open, no return was filed late, and no property interest is involved. If you are a company, measure from the end of the financial year, not from the invoice date.

What you do not do: delete everything that has been quiet for a long time. A customer from four years ago is not rubbish — old is not a reason to delete. Purposeless is.

And what no software can decide for you is whether a particular document is a record within the meaning of the tax legislation. Your accountant will place it better than any system, and where property or an open Revenue inquiry is involved, ask before you clear anything out.

What this means for the system you use

Two capabilities, and it is worth checking yours before you start rather than halfway through.

The first is merging. If your system has no merge, accept that and plan for handwork — copy the history across by hand, then delete one. Nermio has no merge function, so that is exactly how duplicates are handled there.

The second is what happens to an invoice when you delete a customer. Nermio takes a deliberate line here, and it is not the obvious one: a company that has any invoice attached — even a draft — cannot be deleted at all. The record that your six years depend on is protected by refusing the deletion, not by quietly detaching it. A company with no invoices does delete, and when it does it takes its contacts, deals, tasks, notes and whole timeline with it, with no undo. Worth knowing before you click.

And then never again

An annual big clear-out means you work with a dirty list for eleven months. Better that it stays clean by itself, and three habits are enough:

Whoever rings, checks the contact. One sentence at the end of the call, and the field is current.

Search before you create. By phone number, not by name — that is the one search that prevents a duplicate.

Deleting belongs to closing, not to tidying. When a prospect goes to lost and there were only notes, delete them there and then. Then the pile that takes two hours never builds up again.