BNZ has launched an online banking platform for small businesses to help them better manage their cash flow.

The program, designed by BNZ, is believed to be the first of its kind offered by a New Zealand-based bank.

It gives small businesses an 80 per cent advance on any invoices loaded into the system. The remaining 20 per cent is paid when the invoice has been paid in full - usually on the 20th of the month after it has been sent.

BNZ partners director Anthony Healy said the program allowed businesses to escape the "catch 22" of having to wait to be paid before they could fund everyday activities such as expansion, investment, employing more staff or buying materials.

"With Invoice Finance we've taken a realistic view of how businesses actually operate and tailored our solution to fit their needs. The bottom line is it will help them free up cash flow when they need it, so they can get on with the already difficult task of running a business instead of juggling finances."

The program can fund invoices for goods sold in Australia - as long as the goods are sold in NZ dollars - and is compatible with 29 accountancy software programs. Healy said the economy was slowly recovering but was still tough for small business owners looking to grow their companies and cut costs where possible.

He said about $65 million was available for businesses in this category and the bank planned to double that within 12 months. The 500 or so businesses using BNZ's old platform would be transferred to the new program.