Ballots must be in by 8 p.m. Friday, and can be dropped off at nine offices throughout the region.
Chief electoral officer Keith Archer said Wednesday that Elections BC will make the results public in late June after sending them to the speaker of the legislative assembly.
Over 1.56 million ballot packages were mailed to registered voters in Metro Vancouver starting mid-March.
Residents have the option of paying a half-per-cent sales tax to fund $7.5 billion in transportation projects that include more buses, roads, light rapid transit and a new bridge.
The Yes side has tried to woo voters by saying traffic congestion will only get worse in the growing region while the No forces have said residents don't need a tax grab.
Vancouver Mayor Gregor Robertson, who has been sporting a Vote Yes button, is among the biggest supporters of the tax hike as chairman of the Mayors Council on Regional Transportation.
He has said transit improvements will benefit the environment in a city with a growing population.
The Greater Langley Chamber of Commerce is the province's only chamber to oppose the transit tax, said spokeswoman Kristine Simpson.
She said the group supports the No side over concerns that residents will go to nearby Abbotsford, outside the region, to buy big-ticket items such as cars to avoid paying the tax. Abbotsford, which doesn't have a fuel tax, already draws people to fuel up there.
Simpson said the chamber's decision to oppose the transit tax was heavily debated by the board.
"It was a very close vote in December," she said, declining to provide details.
"There are a lot of challenging issues and we spent a lot of time on it. In the long term we will potentially have light rail in Langley, which would be great. But it's a long wait so in the short term it's hard to see how we would benefit by paying the tax."
Simpson said the transit tax was a big topic of discussion at the three-day B.C. Chamber of Commerce AGM, which ended Tuesday and drew about 150 delegates to Prince George, B.C.
Jordan Bateman, spokesman for the B.C. wing of the Canadian Taxpayers Federation, said his group has spent $40,000 opposing the tax hike, while supporters of the tax have shelled out millions of dollars to get out their message.
The Yes side did not return calls for comment.