More than 70,000 people are expected to attend the Download Festival, headlined by Kiss, Muse and Slipknot.
Police said there had been dramatic falls in theft in past years and the wrist tag payment system was one of several ways of keeping this going.
While some fans had reported problems with the technology, organisers said it worked in the vast majority of cases .
Police have reported consistent falls in crime, with last year alone seeing a 70% drop in theft.
The wrist tags are topped up with credit to be used at the various stalls across the site and mean both customers and businesses do not have to carry cash.
Most people have welcomed the innovation but some said the tags had not worked leaving them without access to food and drink.
Organiser Live Nation said it estimated 1% of users had experienced problems and extra help desks had been laid on.
Sgt Ian Weston, who will be patrolling the site in plain clothes, said: "Our main concern is theft from tents, persons and vehicles, so we give out a lot of advice about using lockers and such.
"Intelligence looks at the organised gangs across the country and establishes which festivals they are going to and we build a strategy to deal with that."
Sgt Richard Jordan, a motorcycle officer, said: "From lunchtime (on Friday) it will become very, very busy and the road network sees a lot of strain especially at the beginning and end of the day.
"Unless you need to come here or the airport avoid the area and if you come, expect delays."
A cashless payment system is being used at a Leicestershire rock event in an effort to cut crime.