The 39-year-old surveyor from Uxbridge, west London, was stopped on Sunday while driving his car.
Inside the vehicle were 250 Covid-19 testing kits.
He was arrested under the Fraud Act 2006 after making false and misleading claims about the capability of the tests.
He told investigators he was planning on selling the kits to construction workers. He was released on conditional bail.
Nikki Holland, NCA Director of Investigations, said: “Criminals capitalise on fear and anxiety and they will exploit any opportunity, no matter how awful, to line their pockets.
“Illegally selling testing kits completely undermines the nation’s collective response to the pandemic and actually endangers lives.
“Anyone thinking of trying to profit in this way should take note of these arrests and that bringing these offenders to justice and ceasing their activities is a key priority across law enforcement.”
Graeme Biggar, Director General of the National Economic Crime Centre, said: “Covid-19 is increasingly being used as a hook to commit fraud – and we think these offences are likely to increase during the pandemic.
“Individuals and businesses need to be fully prepared for criminals trying to turn the pandemic to their advantage by scamming them out of money.”
Tariq Sarwar, Head of Operations for Enforcement at the Medicines and Healthcare products Regulatory Agency (MHRA), said: “There are no CE marked tests for home use, and it is illegal to supply such products.
“The safety, performance or quality of the products cannot be guaranteed and this poses a health risk.”