An invoice or bill is a commercial document issued by a seller to the buyer, indicating the products, quantities, and agreed prices for products or services the seller has provided the buyer. An invoice indicates the buyer must pay the seller, according to the payment terms. wikipedia.org

A Bank reconciliation is a process that explains the difference between the bank balance shown in an organisation's bank statement, as supplied by the bank, and the corresponding amount shown in the organisation's own accounting records at a particular point in time. wikipedia.org

QuickBooks is a line of business accounting software developed and marketed by Intuit. wikipedia.org

Sage 50 Accounting is a business management software subscription-based product published by Sage Group. wikipedia.org

Wave Accounting is a free software-as-a-service (SaaS) accounting platform supported by a contextual advertising model. Its target audience are small businesses and self-employed individuals. It focuses on ease of use, task automation, and collaboration.

Customer support is a range of customer services to assist customers in making cost effective and correct use of a product. It includes assistance in planning, installation, training, trouble shooting, maintenance, upgrading, and disposal of a product. wikipedia.org

Zendesk provides web-based help desk software with a support ticket system and a self-service customer support platform. wikipedia.org

Chat technical support is a form of technical support delivered via online chat. Online chat refers to a kind of communication over the Internet that offers an real-time direct transmission of text-based messages from sender to receiver. wikipedia.org

Xero is an online accounting software product for small and medium-sized businesses, as well as for personal finance. The product is sold by subscription (a distribution model commonly known as Software as a Service or SaaS) requiring the payment of a monthly fee. wikipedia.org

Bookkeeping is the recording of financial transactions. Transactions include sales, purchases, income, receipts and payments by an individual or organization. Bookkeeping is usually performed by a bookkeeper. wikipedia.org