What to cover
- Your personal ID number: citizen service number, social security number, national insurance number, whatever your country calls it. On many ID cards it's on the back, on a passport it's on the photo page.
- The lines of code at the bottom (the ones with <<<), if the recipient doesn't need them. On some documents they include that number.
- Your photo, if they don't need to see your face.
In many countries only organisations with a legal reason, like your employer, bank or the tax office, may use that number. A landlord or webshop usually isn't one of them. When in doubt, ask why they need it.