Invoice System Research

A very basic invoice system would typically have the following features:

Core Invoice Management

• Create invoices — line items, quantities, unit prices, subtotals, tax, and totals
• Invoice numbering — auto-incrementing, unique reference per invoice
• Invoice statuses — Draft, Sent, Viewed, Paid, Overdue, Cancelled
• Edit & delete invoices — with audit trail ideally
• Due dates

Client/Customer Management

• Create clients
• Store client details — name, email, phone, billing/shipping address
• Link invoices to clients
• View invoice history per client

Payments

• Record manual payments (cash, EFT, bank transfer)
• Payment gateways (Stripe, PayPal, etc.) for online pay
• Partial payments and balance tracking
• Mark invoice as paid

Items / Products & Services Catalogue

• Reusable line items with preset prices and descriptions
• Tax rates per item or globally

Tax Handling

• Apply tax rates (VAT, GST, etc.) per line item or invoice-wide
• Tax-inclusive vs tax-exclusive pricing

Sending & Communication

• Email invoices directly to clients (with PDF attachment)
• Customizable email message
• Client-facing view link (web portal)

Recurring Invoices

• Schedule invoices to auto-generate weekly/monthly/yearly
• Auto-send on schedule

Basic Reporting

• Revenue summary (paid vs outstanding)
• Overdue invoices list
• Client revenue breakdown

Branding & Customization

• Add your logo
• Custom colors or template
• Custom footer notes / payment terms text

Accessibility

• Mobile-friendly or mobile app
• PDF export / download

Company Profile

• Company name
• Address
• Phone number
• Email
• Logo upload
• Tax/VAT number

Advanced Invoicing system are not really invoices, there are more like a system that also have invoicing.
QuickBooks is an accounting platform that includes invoicing so when a customer pays an invoice QuickBooks automatically updates accounting records and financial reports.

Customer Management

• Customer database
• Customer contacts
• Customer transaction history
• Customer balances
• Customer notes

Invoice Management

• Features
• Create invoices
• Edit invoices
• Duplicate invoices
• Recurring invoices
• Invoice templates
• Custom branding
• Custom invoice numbering
• Multi-currency invoicing
• Tax calculations

Estimates & Quotes

• Create estimates
• Send estimates
• Convert estimate to invoice
• Track estimate status

Payments

• Credit card payments
• Debit card payments
• Bank transfer payments
• Automatic payment reconciliation
• Partial payments
• Payment tracking

Accounting (the main thing of this system)

• General ledger
• Chart of accounts
• Bank reconciliation
• Profit & Loss
• Balance Sheet
• Cash Flow Statement
• VAT tracking
• Expense tracking

Reporting

• Revenue reports
• Sales reports
• Customer reports
• Outstanding invoices
• Tax reports
• Profitability reports

Inventory

• Product tracking
• Inventory counts
• Stock valuation
• Purchase orders

FreshBooks focuses more on freelancers, consultants, designers, developers, and agencies and it does that by incorporating:

Estimates

• Create estimate
• Online approval
• Client feedback
• Convert estimate to invoice

Time Tracking

• Start/stop timer
• Manual time entry
• Team time tracking
• Track time per project
• Track time per client
• Bill tracked hours

Client Portal

• Clients can:
  • View invoices
  • View estimates
  • Pay invoices
  • Approve estimates

These features make this platform worthwhile for freelancers, software developers, consultants, marketing agencies and design agencies.

Jobber is another platform but this time designed for businesses that send workers into field (plumbers, electricians, cleaners and etc).
Its features:

Quoting System

• Professional quotes
• Optional upgrades
• Online approvals
• Automated quote follow-ups

Scheduling

• Calendar scheduling
• Drag-and-drop scheduling
• Team assignment
• Route planning
• Rescheduling

Dispatching

• Assign technicians
• GPS routing
• Job instructions
• Job checklists
• Photo attachments

Work Orders

• Job creation
• Job status tracking
• Work instructions
• Attachments
• Checklists

Customer Communication

• Appointment reminders
• On-my-way notifications
• SMS updates
• Email updates

Invoicing

• Features
• Create invoices
• Mobile invoicing
• Online payments
• Deposit collection
• Partial payments

Client Hub

• Customers can:
  • Request jobs
  • View invoices
  • Approve quotes
  • Pay invoices
  • Track service history

Housecall Pro is similar to Jobber but one feature that make Housecall stand out is:

Marketing (they do it on behalf of the customer)

Features

• Email campaigns
• Review requests
• Customer follow-ups
• Automated messaging