Keeping your invoices: what Keyio stores and what you must keep on paper
How long invoices must be kept, which ones are already electronic, and why a photo in Keyio does not let you throw the paper away.
How long to keep them
The tax office can review a tax return for 4 years from the end of the filing period, so the invoices behind it must be kept at least that long. A business (company or self-employed) must keep its books and supporting documents for 6 years under the Commercial Code. The invoice for something you amortise — the purchase of the property, furniture, an improvement — is needed for as long as you amortise it, and 4 more years after the last return that uses it.
Invoices that arrive as PDF are already electronic
An invoice the supplier sends you as a PDF — by email, or downloaded from their website — is an electronic invoice: there is no paper original. What you must do is keep that file intact and readable for the period above. Attaching it to the expense in Keyio, or forwarding it to the invoice inbox, keeps the file exactly as you uploaded it.
Paper invoices: keep the paper
A photo or scan of a paper invoice is a useful copy — Keyio reads it, files it and keeps it with the expense — but it does not replace the paper. Spanish law only lets you destroy a paper invoice after digitising it with software certified by the tax office (Orden EHA/962/2007), which signs every image electronically. Keyio is not certified software, so keep paper invoices in a folder for the whole period.
This is general information, not legal advice: check with your tax adviser how long your own invoices must be kept.
Keeping a copy of your own
On a property's Expenses tab, More › "Download original invoices (ZIP)" downloads every invoice attached to the year's expenses, named by date, supplier, invoice number and amount, with an index (indice.csv). The index carries each file's SHA-256 fingerprint: if a copy you keep elsewhere gives the same fingerprint, it is byte for byte the file Keyio held.
Deleting an expense removes its invoice from Keyio too, so Keyio asks for confirmation and reminds you to download it first if you have no other copy.