Bradford-based Provident Personal Credit Ltd employed third party companies to send 999,057 unsolicited text messages to promote personal loans
The Information Commissioner's Office (ICO) imposed the fine as the recipients had not agreed to receive the messages.
The BBC has contacted Provident for a response.
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An investigation was launched by the ICO after the regulator received 285 complaints to a spam reporting service between April and October in 2015.
The watchdog said it thought the number of texts sent was higher than the one million figure "as it is likely that other affiliates sent out many more".
ICO head of enforcement Steve Eckersley said the law was clear.
"You can't send marketing texts to people who have not signed up to receive them," he added.
"Being bombarded with texts you didn't ask for and don't want is an intrusion into people's privacy, an irritation and, in the worst cases can be upsetting.
"Companies have no excuse whatsoever for sending nuisance texts, whether they do it themselves or employ someone else to do it for them."
Provident has the right to appeal against the fine.
A credit company has been fined £80,000 for sending nearly one million nuisance texts in six months.