The ICO this week issued final penalty notices to 100 organisations, and has sent more than 900 'notices of intent to fine' since September to organisations that include an unspecified number of GP practices.
Fines levied by the ICO can range up to in excess of £4,000 - but because fines are weighted to reflect the size of the organisation, most practices are likely to fall into categories that could be fined between £400 and £600.
Organisations in the lowest tier - with turnover of up to £630,000 or up to 10 employees - can be fined £400 for failing to pay their £40 annual fee, while those in the next tier up - with a turnover of up to £36m or up to 250 employees - can face a £600 fine for failing to pay their £60 annual fee.
The ICO says that 'all organisations, companies and sole traders that process personal data must pay an annual fee to the ICO unless they are exempt' - with fees set by the government to fund the watchdog's work.
ICO deputy chief executive Paul Arnold said: 'Following numerous attempts to collect the fees via our robust collection process, we are now left with no option but to issue fines to these organisations. They must now pay these fines within 28 days or risk further legal action.
'You are breaking the law if you process personal data or are responsible for processing it and do not pay the data protection fee to the ICO. We produce lots of guidance for organisations on our website to help them decide whether they need to pay and how they can do this.'