Hasmukh Shingadia - owner of the Peaches Spar shop in Upper Bucklebury, Berkshire - claimed that the amount of cash-in-hand at a post office branch inside his shop was greater than the true figure, BBC reported.
Shingadia pleaded guilty at the Oxford Crown Court to a charge of false accounting between December 2008 and March 2010.
His lawyer Nigel Daly told the court his client was suffering a cash flow problem at the time with the non-post office side of his business.
Shingadia, however, pleaded not guilty to one count of theft of 16,180 pounds.
Though the judge granted him bail until a sentencing hearing July 21, he said all sentencing options remained possible.
"I am giving you no indication of what the likely sentence will be in relation to this," the judge was quoted as saying.
Shingadia recently attended the royal wedding as a guest of the Middleton family. William and Kate used to be clients at his shop near the Middleton's family home.
