United States
How to make an invoice: the nine parts of a US invoice, step by step, on an annotated example.
US invoices: sales tax by state and locality, Form W-9, and the usual details.
Freelancers in the US: bill by the hour, subtract a deposit, get paid by check, ACH or Zelle.
Payment reminders: two ready texts to chase an unpaid bill, by WhatsApp or email.
Numbering: one series per document type, and what the UK and France write about it.
United Kingdom
UK VAT invoices: the details HMRC lists for a full or simplified one.
Sole traders in the UK: billing before you have a VAT number.
Canada
Canada: GST/HST, QST and PST by province, with the $100 and $500 thresholds.
Gulf
UAE tax invoices: the details of a full one, and when your TRN changes the title.
Saudi e-invoicing: what ZATCA's FATOORA asks for, and why a PDF is not an e-invoice.