The King of Code contest is sponsored by Windows Phone and is open to developers on any mobile platform.

Meet Antonio Revaliente, VentureBeat’s first King of Code finalist. Leading the team that builds successful mobile invoicing application iFacturas for Windows Phone 7 and the iPhone, Revaliente has proved himself to be a young titan in the global financial app scene.

iFacturas offers mobile billing in Norway and Spain and is quickly becoming an essential app for independent professionals and small business owners looking to invoice clients on the go — which these fast-paced individuals almost always are. With iFacturas, they are able to bill people sooner so they can get paid faster.

Today, Revaliente’s team offers a free version of iFacturas, and a full-featured version that costs $10 a month after free download. This user-friendly model earned it the No. 21 spot on Innovate!100’s list of most promising high-tech startups in the world. And the app’s footprint is certain to grow when it launches in Spain and the United States in the fall.

“The main reason for our success is that we have been able to create a portable invoicing system with a very intuitive user interface,” said Revaliente. “Any professional can easily and rapidly create and send bills using his or her smartphone.”

Not content to provide core invoicing functionality alone, Revaliente led his team to bake in a range of unique features that rely on mobile devices. For example, GPS is used to automatically select clients to bill based on location. When visiting a client for the first time, users can simply hit “get address” to skip entering that client’s location manually. Phone cameras also come in handy, allowing the app to add pictures of service offerings or products to invoices for extra detail.

“Every time one of our users creates an invoice, the iFacturas system creates all of the accounting behind it automatically,” Revaliente said. “That makes us different from other financial apps on the market.”

Revaliente’s team will not stop with iFacturas. The goal is to create a portfolio of financial mobile apps to manage accounting, accounts payable, expense reports and stock management. Users will be able to pick and pay for only the tools they really need. And eventually, iFacturas and more will be available on the iPad platform too.

For now though, Revaliente is very happy with his current development platforms: iOS and Windows Phone.

“We started developing for Windows Phone from the very beginning, long before the device was on the market — and it was sort of a personal bet,” he said. “I considered that Microsoft really wanted to catch up to existing smartphone software and the apps market.”

So far so good. When Revaliente contacted Microsoft in Spain to open up distribution there, he was immediately offered all of Microsoft’s technical resources to help the app get up and running. This support allowed the company to build and style the app exactly how they envisioned it. They are also very excited by the agreement between Windows Phone and Nokia and think that the appearance of Windows Phone software on Nokia devices will mean many more users for iFacturas.

As for iOS: “iOS owns 60 percent of the apps market, so it was a common sense decision,” Revaliente said. “The fact that both platforms provide security is really the key factor for us — we’re dealing with billing and accounting, which is why we will not develop for other platforms like Android or RIM.”

As it prepares for wider distribution, the iFacturas team is collecting international honors. In addition to being recognized by Innovate!100, the app was also selected from a pool of over 3,500 startups to be one of 18 companies to pitch at the European Bizspark Summit in Paris in 2010. Revaliente has also landed an agreement with the largest independent professional association in Spain to get the word out about iFacturas and how it can help contractors and small business owners accelerate their profits.

When it comes to funding, Revaliente’s team is already off to a quick start. It has been selected by Chris Shipley’s Guidewire Group to incubate in Silicon Valley, but it’s still on the lookout for angel investors or first-round venture capital firms to help it set down firm roots in the U.S.

You can find more information on iFacturas at the company’s web site.

Every week, with the sponsorship of Microsoft’s Windows Phone, VentureBeat is crowning the very best mobile developers as “King of Code.” We’re looking for innovative developers who are really pushing the envelope in the mobile space, regardless of the platforms they’re developing on. Enter here for a chance to win a profile on VentureBeat.com, a $1,000 AMEX Gift Card, an Xbox & Kinect Package, and/or a Windows Phone 7 device.