Be transparent – Your client wants to know where their money is going, so don't hide or be too general with line items on your invoices, and be prepared to show receipts. Otherwise, they'll wonder if you're padding the bill. Be specific. For example, instead of listing "materials" as a single expense, list each one on its own line, such as: paint, nails, plywood, etc.
Sales Tax: Depending on your jurisdiction and type of business, the tax requirement can get complicated. Be sure to follow instructions from your local tax bureau and include the appropriate tax amount on the invoice. Pro tip: Use an invoicing software to manage your business activities, change tax settings as you want and make your tax time easier.