Totally get that, most of us don't want a full app for something we use rarely. That's why I kept it as a PWA as it installs in KBs and doesn't take real storage.
On the "having to remember" part: if you've uploaded a receipt once, SlipCrate sends expiry nudges (30, 15, 7, and 1 day before). I can include the app name in the notification so it's obvious where it came from.
I'm also exploring light-touch options so you don't have to remember at all: optional monthly email/push "bought anything new?" reminder, email-forwarding of receipts, or a unique upload address. If you had to pick one "least annoying" flow, which would it be?