Royal Bank of Canada will no longer use U.S. accounting rules to figure its financial results, opting to revert to Canadian accounting standards.

The bank, which is based in Toronto and is the largest in Canada, said the standards in both countries are growing more similar. Royal Bank started using U.S. generally accepted accounting principles (GAAP) six years ago to match the system used by most of its North American competitors. The bank has been producing both U.S. GAAP and Canadian GAAP financial statements, but decided to switch back to the Canadian system starting May 27, Bloomberg News reported.

“Since U.S. and Canadian GAAP have been converging in recent years and there are now significantly fewer differences between the two GAAPs, there is no longer the imperative for U.S. GAAP to be the primary reporting basis,” the bank said in a statement.

Instead of also providing a second complete set of statements under U.S. GAAP, the bank will now provide a reconciliation of material differences in its results under U.S. GAAP in its quarterly and annual statements, the Globe and Mail reported.

The largest remaining difference is in rules covering insurance accounting. Linda Mezan, vice president of external reporting and disclosure, gave the newspaper this example: In the first quarter of this year, the bank reported a profit of $1.04 billion under U.S. GAAP and $979 million under Canadian rules. About $55 million of the difference was attributed to accounting for the bank's insurance businesses.

She acknowledged that analysts have been annoyed by the bank's emphasis on U.S. GAAP. "It was like going out in English and having people come back and say, 'I'm only going to ask you questions in French.' "

In addition, the change back to Canadian rules will save money.

“Having to maintain two sets of records and do all sorts of things to keep track of compliance with U.S. standards and Canadian standards is costly,” said Stephen Spector, a certified general accountant and visiting lecturer at Simon Fraser University in Vancouver. “If they can reduce the amount of effort that's required, they reduce their costs, and these costs aren't trivial.”