Their banks are on lockdown, their supermarket shelves are ransacked and pensioners are sobbing in the street.

But as Greeks go to the polls Sunday — to choose between more belt-tightening or a freefall out of the euro zone — they may only have their cheating selves to blame.

Decades of widespread tax and pension fraud have swindled the country out of tens of billions of dollars a year, a new book claims.

And those frauds have been as brazen and bizarre as they’ve been rampant, according to the book, “The Full Catastrophe: Travels Among the New Greek Ruins,” by James Angelos.

Take the beautiful Greek island of Zakynthos, where almost 2 percent of the population was registered as blind and thus entitled to $400-a-month disability pensions and other charity perks.

That’s a blindness rate some nine times higher than elsewhere in Europe.

Trouble is, the island’s supposedly vision-impaired residents included a taxi driver and a man whom one official described to Angelos as “a bird hunter.”

Among the 680 residents registered as blind in 2011, some 500 weren’t blind at all.

And an astonishing 61 were actually driving around the island, Angelos found.

“It appears the ‘blind’ of Zakynthos saw only the color of money,” the Greek newspaper Ethnos wrote of the scam.

Here’s another scam from Angelos’ book: pensions for the dead.

A recent Greek government investigation — undertaken as part of an anti-fraud crackdown mandated by the country’s creditors — found a highly suspicious 8,500 pensioners had passed age 100.

A closer look showed some 40,000 pensions were being “collected” by people who were no longer among the living.

In a country where even “blind” taxi drivers can collect disability, it came as no surprise to Angelos when he found a treasury employee who remained on his town’s payroll three years after he was sentenced to life in prison for murdering his mayor with an Uzi.

Scams permeate every walk of life — even when Greeks aren’t actually walking.

The subway system serving 5 million Athenians was essentially a free ride.

Athens’ subway has no turnstiles, and riders are expected to pay their fares on the honor system.

Unfortunately for the city coffers, honor is in short supply.

The honor system also falls short when it comes to Greeks reporting their income for tax purposes.

In a country of 11 million people, only 5,000 admitted they earned more than $100,000 a year, the Daily Mail reported.

One economist was prompted by the report to joke that Greece must be “a poor country full of rich people.”

But even when officials try to crack down, the fraudsters go to extreme lengths to outwit them.

A Daily Mail investigation focused on one of Athens’ most exclusive neighborhoods, full of lawyers, doctors and masters of industry.

Only 300 of the area’s homes claimed to have swimming pools, which require owners to pay a luxury tax.

But when officials looked into the low number, using Google Earth to scan the back yards, they found the number of pools to be closer to 20,000.

The fraudsters responded by buying camouflage-print tarps to cover up their pools, the Mail reported.