The Spreadsheet Behind It

Every saved expense becomes one new row in a Google spreadsheet, on the tab the app is set to use. The app only ever adds rows — it never changes or deletes anything already in the sheet. Everything else about the record (fixing a typo, deleting a duplicate, the totals and summaries built on top) happens in the spreadsheet itself, the normal Google Sheets way.

What one row looks like

Each entry fills columns A through H, in this order:

Column	What goes in it
A	Category
B	The USD value (see below)
C	The amount you typed
D	The currency you chose (USD or MXN)
E	The month you chose
F	The expense type (or blank)
G	Your note
H	The date you saved the entry, as MM/DD/YYYY

Column H is filled in automatically with the day you pressed Save — it is not the same thing as the Month in column E, which is the month you booked the expense against.

Do not reorder, insert, or delete columns A–H on the expense tab. The app always writes into these positions, and the sheet’s own calculations read from them. If the columns move, new entries will land in the wrong places without any warning or error.

How MXN becomes USD

The app does not convert currency itself — the spreadsheet does.

• When you save an entry in USD, column B simply gets the same amount.
• When you save an entry in MXN, column B gets a small formula that multiplies your amount by the exchange rate stored in cell M2 of the expense tab.

Because it is a formula, every MXN row recalculates whenever the rate in M2 changes. That is deliberate: one rate, kept in one cell, applied consistently to every MXN entry.

Updating the exchange rate

What you do:

1. Open the spreadsheet (the blue Sheet: link at the bottom of the app).
2. Go to the expense tab the app saves to.
3. Click cell M2 and type the current MXN-to-USD rate.
4. Every MXN entry’s USD value updates on its own. There is nothing to change in the app.

Fixing a mistake

There is no edit or undo in the app. If you saved something wrong — wrong amount, wrong month, a duplicate — fix the row in the spreadsheet.

What you do:

1. Open the spreadsheet from the blue Sheet: link at the bottom of the app.
2. Find the row (new entries are added at the bottom; column H shows the date each one was saved).
3. Edit the cell that is wrong, or delete the whole row for a duplicate.
4. If you are correcting an MXN entry’s amount, change column C (the amount) — leave column B alone, since it is a formula that recalculates by itself.

You can also type rows straight into the sheet by hand when that is easier — the app does not mind, and nothing breaks, as long as you follow the same column order.