Everything runs on your phone, so most problems are solvable right there. Start here; if it isn't covered, email sivavimelrajhen@gmail.com and include what you were doing and what happened.
Export a statement from your bank as CSV, OFX/QFX or QIF, save it to Files or iCloud Drive, then in the app: + → Import a statement. Choose the account it belongs to. Nothing is written to your books until you have seen the preview, and the app tells you which rows it thinks are already on record.
If the columns are read wrongly, fix them on the preview screen — the picker lists your file's own headers.
+ → Scan a receipt. The app reads the merchant, date, total and tax, and shows how confident it is about each one and where it read it from. If the charge is already in your books it offers to attach the receipt to it rather than creating a duplicate.
Open the transaction. The card under "Category" says exactly what decided it — a rule, your own history, a category keyword, or the on-device model — how confident it was, what else it considered, and which of your past entries it leaned on.
Correct it once, then use "Always file … here" on the transaction. That writes a rule, and rules run before the model and are never overridden by it. You can also add a word to a category's keyword list in More → Categories, which steers everything containing that word.
More → Settings → How much to decide for you. The first slider is the bar the app has to clear to file something without asking; the second is the point below which it stops offering a suggestion at all. Lower the first for less reviewing and more mistakes; raise it for the reverse.
The first run after a large import does the most work, because there is no history to learn from yet. It gets much faster as your books fill up: repeat merchants are matched without the model at all. You can leave the screen while it runs, and cancel it at any time.
Numbering, prefix and payment terms live in More → Your business. Each invoice can produce a PDF to send and a UBL 2.1 XML e-invoice file for portals that want one. Recording a payment can also post the deposit to a bank account, which keeps your balances and your invoices in step.
The app produces the file; submitting it to a tax authority is done by you, through their portal.
More → Export everything → Complete backup (JSON) gives you a file that restores everything exactly, including settings for each record. On the new phone, install the app and use Export → Restore from a backup file. The ZIP export additionally contains every receipt image and invoice PDF.
More → Imports lists every file you have imported, with an Undo that removes exactly the transactions that came in with it.
Check More → Accounts. If a statement stated a closing balance that no longer agrees with the entries on record, the app says so and by how much — usually a missing statement or a duplicated row.
It helps you keep books. It is not an accountant, it does not file returns, and its tax summary is a calculation from the tax codes you assigned — check it against your own return before submitting anything.