The system, called Mobile POS, is being used by Neilson's representatives to take credit and debit card payment details and obtain authorisation within 15 minutes using text messaging.
The company is using it to sell extra activities on holidays, such as excursions and entertainment trips.
To get payment authorised the sales rep texts the customer's payment card details to a secure server belonging to service provider Adelante.
This triggers a request for authorisation from the customer's bank and a reply is sent back to the sales rep within 15 minutes.
Andy Boyce, overseas systems manager for Thomas Cook Tour Operations, said, "We have already noticed major benefits. The SMS transaction service has reduced our administration cost. Mobile POS is inexpensive to deploy and improves cashflow by processing transactions at the earliest possible time. The system also proved very easy for our staff to use."
Firms using Mobile POS can manage it via a browser, which allows end-users to be added or removed; set permissions; perform office-based payments and refunds; and generate reports.