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Guide

What Is a Suppression File? Stop Paying for Data You Already Have

A suppression file is a list of people who should be taken out of your data before you receive it — usually your existing customers and anyone who has asked not to be contacted.

What goes in it

  • Your current customers (so you don't pay for them again).
  • Everyone who has opted out or said "do not call".
  • Records you've already bought.

Industry files such as the TPS (calls) and the Mailing Preference Service (post) are suppressions too.

Why it matters

It saves money, avoids annoying existing customers with "new customer" offers, and is the easiest way to honour opt-outs across every list you buy.

Suppression at DataMembership

Upload your suppression file (CSV, Excel, TXT or ZIP) in your login. We remove anyone in it before every delivery, on memberships and one-off orders — and we never send you records you've already had.

Questions

What format should my suppression file be?

CSV, Excel, TXT or ZIP, with phone numbers and/or names and postcodes.

This guide is general information, not legal advice. For the full rules see the Information Commissioner's Office (ico.org.uk). Last updated October 2026.