Flood-damaged businesses in northern New South Wales say promised disaster assistance is taking too long.

"I'm not getting any sleep — completely, utterly stressed," North Lismore saw miller Kristen Gardner told 7.30.

"I can't ask them to repair something that can't be paid for."

Mr Gardner's saw-milling and essential oil production business is barely surviving.

Ten weeks ago the flood waters came well over the roof of his workshop, destroying all of his paperwork, computers, and damaging much of his valuable machinery.

He applied for two small business flood assistance grants of up to $50,000 six weeks ago.

He finally received word the application was approved on Tuesday — less than a day after 7.30 asked the NSW Department of Customer Service why the application was taking so long.

Mr Gardner said the delay had taken a toll.

"Unfortunately, we actually needed help six weeks ago … nobody understands until they come here and see how bad it really is," he said.

The Lismore Chamber of Commerce and Industry said it had come across a "significant number" of cases where funding assistance has been delayed to businesses devastated by the record-breaking floods in February and March.

"[It's] very frustrating — [the government is] asking for a lot of information that can be verified in other ways," chamber president Ellen Kronen said.

Ms Kronen owns a retail business that was damaged and said she had first-hand experience with how long it takes to receive government assistance.

The chamber of commerce secured some funding after an eight-week wait.

"We're three months in and I don't know of any business that will have cash in the bank that will sustain them," she said.

"A $50,000 grant really doesn't go very far but it does make a difference.

"It might help keep a staff member on or it might help to pay for all of the extra cleaning."

Most shops in the Lismore CBD remain closed.

"Let's say in just the CBD alone there would be 1,000 businesses at least — so maybe 50 of those are operating again," Ms Kronen said.

North Lismore businessman and owner of Medicine Garden Australia Stephen Bernier said government bureaucrats do not understand what is happening on the ground.

He lost much of the stock in his herbal and tea business and has recently applied for a small business assistance grant.

"It's out of their league … they're just used to shuffling paper. This is real work," he said.

"The government has to plan that extraordinary events are going to happen."

In a written statement to 7.30, a spokesperson for the NSW Department of Customer Service said more than 223 assessors were working seven days a week to urgently assess grant applications.

"There have been over 34,011 applications for funding across the flood support grant streams supported by Service NSW this year, indicating the sheer scale of the disaster faced in over 60 local government areas in NSW,” the statement said.

"Of this 4,185 grants have been paid with over 95 per cent positive feedback from our customer service feedback. Another 1,162 are due to be paid via their financial institutions shortly.

"Due to high numbers of applications being incomplete or requiring additional verification, Service NSW staff make additional inquiries before all grants decisions are finalised.

"In addition, Service NSW has identified more than 1,775 cases ($22 million) of suspected fraud across all calendar year 2022 flood grants as at 9 May which are under fraud review.

"In the last 48 hours we have also made changes to make the process simpler for sole traders so they are able to have their applications streamlined and assessed more quickly."