Tests carried out by the National Standards Authority last year have shown that 31% of taxi meters and 21% of weighing scales in shops failed those checks.
Speaking on RTÉ's Morning Ireland, NSA Chief Executive Maurice Buckley said despite these figures it is not always a case of people being overcharged on purpose.
Mr Buckley said instruments can sometimes drift out of compliance or get damaged and have to be recalibrated.
"There needs to be that policing system there all the time just to make sure everything is kept right and proper. And our job is to make sure that the quantity you get is the quantity you pay for."
He said there is always the risk that meters have been tampered with and that people have been prosecuted as a result.
Taxi meter checking is now tied in with the renewal of licences and Mr Buckley said, so far, the compliance rate for 2015 for taxi meters is "superb" with 16,000 out of 17,000 to be rated as fully-compliant.
