Late payments are inevitable as a freelancer, but you may take efforts to avoid them.
Request payment in advance. Set aside a portion of the whole amount and ask for it in advance. While you're working, you'll have at least a piece of the money in your pocket. This also makes scheduling time for this client's work easy.
Submit your project in milestones. Builders, like those who work on houses, demand payment as the work is done. You can follow suit. You may divide it up any way you wish, but a frequent example is 35% upfront, 35% halfway through, and 30% at the end. This guarantees you are paid along the way, and if they don't, you may put a hold on ultimate delivery.
Allow the customer to pay for expenditures incurred while performing work for them. If you generate expenses while executing work for your client, allow paying for them directly. If you pay them in advance and include them in their invoice, they might refuse to pay, claiming they were unaware of the charges.
Work on a contract basis all the time. Don't rely on verbal agreements or make the assumption that a client will pay. If you don't have everything on the paper, you won't be able to stand up in court.
Do your homework. To find out about a prospective client's reputation, do some research. Move on to the next possible client if you notice a pattern of businesses complaining about not being able to pay their invoices.
Without regular payments, no business can function. It's critical to set your company up for success from the beginning. Start with a contract that lays out the limitations for missing or late payments, no matter how happy you are to acquire that first customer or earn a "big deal."