Keeping a Client Database: From Excel to a System
A client database is the structured list of all clients and their contacts, with per client the details you need to deliver, invoice and stay in touch. Almost every company starts with one in Excel, and that is not a bad start: a well-designed spreadsheet works longer than most vendors would have you believe. This article covers how to build and maintain a client database properly, at what point the spreadsheet stops being enough, what the GDPR requires of you, and how to move the file to a system without hassle.
What belongs in a client database
The mistake most files make is not that too little is in them, but that too much is in one column: "John Smith, 07700 900123, call after 1 Sept" in the Contact field. Put each piece of data in its own column, so you can filter, sort and import on it later.
| Group | Fields |
|---|---|
| Organisation | Company name, company registration number, VAT number, visiting and billing address, website |
| Contact | First name, last name, role, email, phone, and which organisation they belong to |
| Classification | Relationship type (client, prospect, supplier), industry, source, account manager |
| Agreements | Payment term, rate or discount agreement, invoice language, reference on the invoice |
| History | Date of last contact, what was discussed, next action |
| Housekeeping | Date created, last changed by, active or archived |
Two rules that save a lot of grief: one row per contact (not per organisation, because a client has several) and the company registration number as the fixed key, so that "Baker Ltd" and "Baker Limited" do not become two clients.
Building a client database in Excel
Work with two sheets: Organisations and Contacts, where each contact refers to its organisation via the registration number or your own client number. Turn both into a real Excel table (Insert, Table), so filters and new rows follow automatically. Use data validation for relationship type and industry, otherwise within a month you have "client", "Client" and "client " side by side. And never store history by overwriting a cell: add a row on a third sheet, Touchpoints, with date, person and note.
Set up like that, a client database in Excel is fine up to roughly a hundred organisations and one person maintaining it. After that it starts to pinch, and always in the same four places.
Where the client database in Excel breaks down
1. Versions appear. As soon as the file is emailed or someone puts a copy on their desktop, there are two versions of the truth. After six months nobody knows which is the latest, and the account manager who just entered a new phone number did so in the wrong one.
2. The history does not fit. A spreadsheet is a list, not a timeline. Who spoke to whom last year and about what lives in mailboxes and heads. When the account manager leaves, the history leaves with them.
3. No link to money and work. The file does not know which invoices are outstanding, which project is running and how many hours were logged for this client last year. You answer those questions next to the file, in accounting and time tracking, and that is precisely the work you wanted to save.
4. It cannot be accounted for. A file with personal data on a laptop, shared by email, without a log of who changed what and when: in a data breach or an access request there is little you can show.
What the GDPR requires of a client database
A client database contains personal data (name, business email address, phone number of contacts) and therefore falls under the GDPR, even if it only concerns business contacts. Four things to consider in any case:
- Legal basis. For data of clients and their contacts this is usually performance of the contract or legitimate interest; for emailing prospects it is more delicate.
- Record of processing activities. You must be able to show which data you keep, why and for how long. A client database is a processing activity that belongs in that record.
- Retention period. Fiscal records (invoices, and thus the client data on them) are kept for the statutory period, seven years in the Netherlands; for contacts of former clients and for prospects who never became clients there is no statutory period, so set one yourself and actually clean up.
- Security and access. Who can get in, and can you prove it? With a system with accounts and a data processing agreement that is a matter of a list; with an emailed Excel file it is not.
This is general information (as of mid-2026), not legal advice. Consult a privacy lawyer or your supervisory authority for your own situation.
From Excel to a system in four steps
1. Clean up before the move. Every error in the file will be in the system afterwards. Remove archived clients you no longer need, fill in missing registration numbers and make the relationship types unambiguous. This is also the moment to apply the retention period above.
2. Deduplicate. Sort by registration number and by company name without legal form, and merge duplicate organisations. Do the same for contacts by email address.
3. Split into the parts the system expects. Usually that is organisations and contacts as two separate files, with a reference from the person to the organisation. A good system provides a sample file per part with the expected columns; stick to it and the import goes right first time.
4. Trial import, then the real thing. Import a small part first, check that the fields land in the right place, and then do the rest. An import that deduplicates is worth its weight in gold here: if the second attempt does not create duplicate clients, you can start over without fear.
In Horixa it works exactly like that: organisations, contacts and later also projects, hours and invoices are uploaded as Excel or CSV files, with a sample file per part, and re-importing does not create duplicates. The step-by-step plan is in switching project management software.
What you get back afterwards
The difference between a client database and a relationship database is not the list, but what hangs off it. In a system, the projects, the logged hours and the outstanding invoices of that client sit on the same page as the client details, and with a mailbox connection the history fills itself. What to check when choosing such a system is covered in relationship management software: what it is and what to look for.
Frequently asked questions
What is a client database? The structured list of all clients and their contacts, with per client the details to deliver, invoice and stay in touch: company details, contacts, classification, agreements and history. In a system the same list is usually called a relationship database or CRM.
How do I build a client database in Excel? Two sheets, Organisations and Contacts, with the company registration number or a client number as the key between them; each piece of data in its own column; data validation on relationship type and industry; and history as separate rows on a third sheet instead of overwritten cells.
What is the difference between a client database and a CRM? A client database is the list itself. A CRM or relationship management system is the list plus the history, the contacts with turnover, and the link to projects, hours and invoices. The list is inside it; the system does something with it.
May I keep business contacts in my client database? Yes. Data of contacts at clients is personal data and falls under the GDPR, but performance of the contract or legitimate interest is usually the legal basis. Include the processing in your record of processing activities, set a retention period and make sure you can show who has access.
How do I move my client database to a system? Clean up, deduplicate by registration number and email address, split into organisations and contacts according to the system's sample file, and do a trial import first. Choose a system that deduplicates on re-import, then a second attempt is never a problem.
What does client database software cost? Standalone tools from about €10 per user per month. At Horixa the client database (the CRM feature) is included in every plan; Start costs €109 base licence plus €19.95 per user per month, calculated from five users, so €208.75 per month excluding VAT for a team of five.
Your client database out of Excel and into a system where the projects, hours and invoices of the same client already sit? Try Horixa free for 14 days.