The secret to building a bustling tax practice is to go where the clients are — especially when filing season is reaching a fever pitch.

For Rock & Hammer Tax Service, a New York accounting firm, this means packing up a truck every day, cranking up some rock music and heading to midtown Manhattan.

There, the firm’s accountants field a variety of queries from people on the street.

Questions range from “How do I set up my small business for payroll and sales taxes?” to “I haven’t filed with IRS in six or seven years. Where do I start?”

“They feel more comfortable coming to us,” said Henry Obadiah, senior CPA and co-founder of Rock & Hammer. “We’re low-key. We’re not the suit-and-tie kind of guys.”

The tax truck has been a staple of Obadiah’s practice for the last three years.

“Henry had the idea to start a tax truck as we went through the Midtown Tunnel,” co-founder Roger Gillman said. “He saw a hot dog truck and said, ‘That’s what we need!'”

The pair bought an old Fed Ex truck from a friend in the Washington, D.C., area, ripped out the shelves on the inside and worked with an expert to wrap the vehicle with the accounting firm’s logo.

Gillman and Obadiah initially parked their first truck in the Queens borough, where they also had an office at the time. Back then, they kept a close focus on tax services.

As they grew, the two realized their real niche was to develop a full-service accounting firm and court clients through free consultations at the trucks year-round. Bookkeeping and international tax issues are among their specialties.

“We knew quickly that it was a viable way to retain leads,” said Gillman. One of the trucks can fetch as many as 15 to 20 leads a day, Obadiah said.

Eventually, the pair acquired two more trucks. They also opened offices in midtown Manhattan and Brooklyn, which is where they get to the nitty-gritty of accounting and handle clients’ paperwork.

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As Tax Day — April 18 this year — rolls around, Gillman is looking forward to the warmer weather. New York’s rough winters are one of the largest challenges the trucks face outside.

The other obstacle is parking. Bryant Park, which is in the center of Midtown, is a sweet spot for pedestrian traffic — and street vendors jockeying for parking space know that.

All three trucks are out year-round, and when the weather is brutal, prospective clients are likely to keep on walking.

As the weather heats up, so do the leads for new clients.

“We start blasting the music on the street, it creates a vibe,” said Obadiah. “It’s like a big party out there, especially when it’s toward the end of the week.”