Individual vs. Business Seller Accounts:

• Individual Account: This is primarily for selling personal, second-hand items. It's not intended for selling new goods or operating a business.
• Business Seller Account: This is designed for legal entities who want to sell goods as a business. If you have a limited company (LTD), you should be using a business account. Your LTD should be registered with Companies House or the equivalent in your country.

Selling Plans (Individual Plan vs. Professional Plan):

• Individual Plan: You don't pay a monthly fee but are charged an additional fee (like 90p) per sale. This plan is available to both individual and business account holders.
• Professional Plan: There is a monthly fee (e.g., £30, or £25 plus VAT). This plan is more suited for businesses expecting to sell items regularly.

In your case, if you're operating an LTD, you should transition from an individual seller account to a business seller account. This change will allow you to manage your business more effectively on Amazon, including handling tax information correctly. It's important to understand that the 'Professional' selling plan is just an option within either the individual or business account types, depending on your sales volume and needs.

Regarding adding your LTD to your seller account, this is usually done during the setup of a business seller account where you provide your business's legal information. If you've already set up an individual account, you may need to contact Amazon Seller Support for assistance in changing your account type or adding your business information correctly.