Custom Buttons: In Zoho Books, custom buttons allow you to automate repetitive tasks by creating custom actions for specific modules such as invoices, expenses, and bills. These buttons can be added to the detail view of the modules and can be used to perform specific actions, such as sending an email, creating a PDF, or updating a field.

​Validation Rules: Validation rules in Zoho Books are used to enforce specific conditions or constraints on data entry in a module. For example, you can set a validation rule to require a valid VAT number or to prohibit the entry of negative amounts. Validation rules help ensure the accuracy and completeness of your financial data.

​Workflow Rules: Workflow rules in Zoho Books allow you to automate tasks based on specific conditions. For example, you can create a rule that automatically changes the status of an invoice from "Draft" to "Sent" when it is approved. Workflow rules can also be used to trigger reminders, send notifications, and assign tasks to team members.