What an invoice needs
Your name and contact details, the client's details, an invoice number and date, a list of work with prices, any tax that applies, the total, the due date and how to pay.
Short payment terms
Due on receipt or within 7–14 days is common for small jobs. Offer an easy payment method; every extra step delays payment.
Follow up politely
Send a friendly reminder the day after the due date, again a week later, then call. Most late payments are forgotten, not refused.
Do this today
Make an invoice template with your details and numbering, and decide your standard payment terms.