Your tax year, worked out on this device

If this browser's data is cleared — “clear site data”, a reinstall, a wiped profile — the documents and figures go with it, and there is no copy anywhere else. That is the price of nothing leaving your device. A backup file is the answer: one encrypted file you keep.

Typed once, kept here, and used only to find your own details on a page and paint over them before an image is sent to be read. NI numbers, postcodes, sort codes, account and payroll numbers and dates of birth are found without being typed. Figures, dates, tax codes and your employer's name are never covered.

Your name(s), one per line Your address lines, one per line Anything else to hide

The one thing that leaves this device: the page images of a document, with your details painted out, sent to a relay that passes them to Claude and returns the figures. Nothing is stored there. Leave it empty to keep everything here — documents are stored and wait.

One encrypted file, made and read here. Without the passphrase nobody can open it, including us. Keep it where you keep other important files.