SYDNEY, June 23 (Reuters) - Payments software firm Zeller said on Wednesday it plans to apply for a full Australian banking licence after raising A$50 million ($38 million) from investors led by Spark Capital, an early Twitter (TWTR.N) funder. A spokesman for Zeller said the fundraising, in which existing tech-focused investors Square Peg and Apex Capital Partners participated, values it at A$400 million. A banking licence would allow Zeller to take on Australia"s Big Four banks, which have dominated business lending for decades and are now having to develop simpler and cheaper payment products to compete with new entrants. The Melbourne-headquartered payment software provider, which was founded 18 months ago, sells terminals and software which allow businesses such as stores to accept and manage customer payments. More than 1,500 businesses had signed up in its first month of operations and weekly payment volumes had grown 200% since it launched 6 weeks ago, Zeller said in a statement. "We built Zeller to connect the disparate financial services, payments and banking tools that Australian businesses use every day ... and our partnership with Spark Capital helps us accelerate development of these new products," Zeller Chief Executive Ben Pfisterer said. ($1 = 1.3222 Australian dollars)