In today's competitive market it's vital that your website not only be your branding document, but it also needs to be a portal to many of your operational systems.
For example, when you're offering booking systems on your website these should have a direct integration to your bookings systems in the back office, and ideally these booking systems should have an integration to your financials systems.
Shop merchandise that's offered for sale online should have some integration to your Point of Sale systems. Naturally your POS should automatically update your stock systems and ideally your stock systems should integrate with your financials.
When you're offering a sign up form online this should automatically populate your customer database that you use for your email marketing. One clean database is a must.
These integrations are fundamentally important to your business to not only save you time but also to ensure you're not making any mistakes through double-handling.
So when you're shopping around for a website provider try to find one that specialises in your field, or at least has a thorough understanding of the types of operations systems you have in place. Your website provider should be asking you questions about how your business operates in general, not just about what style you'd like to see on your website. If these questions aren't being asked then I would recommend your website plan is not thorough.