The Institute of Chartered Accountants says it shouldn't take a small firm any more than one hour to do its return and pay all its tax every month.
The institute has released its second paper on ways to simplify the tax system for smaller business.
It argues separate tax systems for small firms and large firms would boost growth and productivity by freeing up the time of small firms to concentrate on their operations.
The institute's tax director Craig Macalister says single traders turning over less than $60,000 and not registered for GST would pay a flat tax of 14%.
He says it would be very simple if they could then fill in a basic form and pay the tax owed at an IRD or bank branch.
Business owners wouldn't have to fill out complicated returns or keep track of expenses.
A rate of 7% would apply to traders selling goods.
The institute also proposes a new model based on GST for businesses with turnover of less than $600,000.
Income tax would be calculated on GST returns and paid every two months.
Mr Macalister says businesses opting to go with one of the new models might pay slightly more tax than they do now but the time and cost of calculating the tax would be reduced.
He acknowledges some institute members might not be happy with a tax system that sidelines accountants, but change is inevitable and the institute is trying to raise the issues now and create some awareness.
He suggests about 48% of businesses would be eligible to sign up to one of the two models.