Marketing Data Supplier: 6 Questions to Ask Before You Choose

A marketing data supplier gives your business direct access to the companies and contacts most likely to convert. If you want to increase sales, you need accurate, targeted data that puts you in front of the right customers. Buying up-to-date, compliant data is one of the most effective ways to find and convert new leads.

Insight Data is one of those companies. We’re experts in the compilation of data, centring on the fenestration and construction industry, and we constantly update our existing records while seeking out newly-formed companies we think will be a good fit for our clients. All this information is uploaded to our Salestracker platform, the UK’s most accurate prospect and marketing data with in-depth market intelligence all online, in real-time.

So if you’re a company looking for more leads, it makes perfect sense to pair up with data suppliers like Insight. However, doing your homework is always a clever idea, and to help you make an informed choice we’ve compiled a list of questions we feel are worth asking any potential data supplier before you get them on board.

1: What is the source of the data?

In an age where the truth of what we read is often highly questionable, it is vital that you have complete faith in your supplier’s knowledge bank. You need to make sure that it is collected from a reliable source, and not harvested second or even third-hand. Here at Insight Data, our trained and experienced call centre staff make more than 20,000 telephone calls a month, checking and updating records. We have data analysts who constantly analyse the quality and accuracy of our information. This means our clients can make informed decisions based on data that is guaranteed to be trustworthy.

2: Is the provider allowed to collect and sell that data?

GDPR and Data Compliance in 2025

The General Data Protection Regulation (GDPR) has applied since May 2018 and still governs how personal data is collected, stored, processed, and sold. Any data supplier you use must be fully GDPR-compliant — and so must you.

A compliant data provider should:

• Clearly document the personal data they hold

• Record how and when it was sourced

• Specify the lawful basis for processing

• Outline how it’s updated and maintained

• Control who can access it

Using non-compliant data puts your business at legal and reputational risk. Always ask for clear evidence of GDPR compliance before working with any supplier.

3: When was the last time the data was updated?

There’s nothing more frustrating for a business chasing leads to discover that emails bounce back, phone numbers have changed, staff have left or even that the lead has gone bankrupt. In other words, the data you’ve been supplied with isn’t fit for purpose.

On average, records on the Insight Database are verified and updated every 90 days. We even credit check the companies on our database for financial stability so our customers can feel confident they’re targeting solvent firms. Plus, we also send more than five million emails a year, which means on average every email address is tested twice a week.

4: How is the data maintained?

We’ve already addressed the issue of how important fresh data is. If the provider states that the data is fresh because it is regularly maintained, it is a good idea to ask how this is done. One of the best ways to check is to request the date stamp records for databases. Data collectors use date stamps to ensure all their records are within an acceptable window of freshness.

5: Has the data been screened against TPS?

The Telephone Preference Service (TPS) allows individuals and sole traders in the UK to opt out of unsolicited marketing calls. By law, you must not make live marketing calls to numbers listed on the TPS unless you have explicit consent to do so.

Screening your call data against the TPS is a legal requirement under the Privacy and Electronic Communications Regulations (PECR), enforced by the ICO.

When sourcing data, ask your supplier:

• Has the data been screened against the TPS?

• When was it last screened?

• How frequently is it re-screened?

Using non-screened data can lead to fines and enforcement action.

6: Are there any clauses in the agreement you are making that you do not share information with a third party?

If you can’t see the ‘no sharing’ clause in the terms and conditions, it’s possible that the data you are buying has been shared illegally with third parties. As confidentiality is a key principle to GDPR compliance, it’s important to ensure that you buy data sets that comply with those laws.

Any reputable list broker should be able to answer every one of these questions. If the seller cannot provide any of the information above, it is highly recommended that you avoid that supplier. It could leave you and your organisation liable. Get in touch today to discuss your marketing data requirements.