"We have no reservations in principle," Harper said Sunday in Dublin ahead of the G8 summit.
But the prime minister added any tax measures would need the approval of Canada's provinces and territories.
"There's no upside to tax evasion. It's bad policy. It's bad politics. And governments lose revenue that governments should be getting," he said.
"Obviously we believe in low tax rates in Canada but people need to pay the tax rates that we actually have. I think the only reservation we will obviously express is that in terms of implementation in Canada, we're going to have to consult with our provinces because we're a federal state and they have taxation powers."
Among the items on the agenda at the annual meeting of leaders of the world's eight richest countries is a British proposal aimed at tackling hidden company ownership.
"This is a very important initiative by Prime Minister (David) Cameron," Harper said.
"It is important that we do it and that we do it together because when we're dealing with tax evasion, we're dealing with problems that cross borders.
"Even the most powerful governments in the world can't deal with these things by themselves so I look forward to being part of the declaration and to making progress on this as we leave the summit."
British Prime Minister David Cameron told Sky News every member of the G8 supports a plan to identify who actually owns companies.
Cameron also wants to create a central registry of company ownership, but tax activists claim Canada and Russia oppose such a move.
The British prime minister says he hopes all countries will adopt public registries.
Harper was to leave Dublin on Monday for the G8 summit in Northern Ireland.
On Sunday, he met Irish Prime Minister Enda Kenny. The two leaders talked about the free-trade negotiations between Canada and the European Union.
"We hope that the discussions that are ongoing will conclude and, of course, the potential and the benefit for both countries, both Europe, Ireland and Canada," Kenny said.
Trade between Canada and Ireland would flourish if a free-trade deal is signed, Harper said.
"Speaking of trade," Harper said, "Ireland, of course, would also benefit from a free-trade agreement between Canada and the European Union."
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