If your company is still in the process of being registered by local government authorities, you can indicate this "in-progress" status in the Company section of your account in place of the legal documents you'll eventually upload once the business has been registered.
While you're waiting for your business registration to be finalized, you can still create and send quotes to potential new clients. Your clients will also be able to accept those quotes and pre-pay for those services.
However, you won't be able to get paid until you've uploaded all relevant legal documents proving your business's registration into your Malt account. Until that happens, the prepaid funds will be kept safe in a digital wallet.