In the books, the hotel's cash is its cash and bank accounts: the ones carrying SAT grouping codes 101 and 102 (the SAT is Mexico's tax authority, and its grouping code classifies every account). Any cash flow you compare against the balance sheet, whether it's the cashier screen, the bank screen or your bank statement, has to land on the balance of those accounts. When it doesn't, the gap has a specific source.
The Estados financieros (Financial statements) screen currently shows the income statement and the balance sheet; the cash flow statement doesn't appear there yet. What you can compare on screen today is the balance sheet against Caja (Cashier) and against Bancos (Banks).
The symptom
The cashier's Flujo de caja diario (daily cash flow), the Según los libros (per books) balance in Bancos or your bank statement don't match what the balance sheet shows for cash and banks. Or the balance sheet itself shows Descuadre de… (out of balance by…) next to its title.
Likely causes, from most to least common
1. The opening entry is missing
The books start with the first póliza (journal entry): the money the hotel already had in the drawer and at the bank doesn't exist for the balance sheet until it's entered. How to confirm: in Balanza de comprobación (Trial balance), the first month shows a zero opening balance for cash and banks. How to fix: post the opening entry with Capturar póliza (Enter entry), using balances as of your start date (Manual entries).
2. Money that moved outside the daily entry
The daily entry carries the charges and payments of the signed day sheet. Expenses paid out of the front-desk drawer, cash taken from the drawer to the bank, and bank fees don't flow in on their own. How to confirm: the daily cash flow (Cashier → History) shows Gastos (expenses) that aren't in the account detail of the cash account. How to fix: each one needs its own entry: the expense through Accounts payable or a manual entry; the bank fee and the cash deposit from Bancos with Registrar como gasto (Record as expense), which asks for the offsetting account and works for both inflows and outflows.
3. Each screen cuts the day differently
The daily cash flow adds up by calendar day and covers only the front-desk drawer. The books use the operating day, with the hotel's cutoff hour, and send each payment to its code's account: if the card code points to a bank account, the payment lands there the day it's taken, even if the bank deposits it days later and net of its fee. How to confirm: compare full months, not single days. A timing window isn't fixed, it's explained (The operating day and its cutoff).
4. Bancos adds what the balance sheet doesn't
The Según los libros balance in Bancos starts from the Saldo inicial (opening balance) you entered when you set up the account, which is not a journal entry, and today it also adds lines from cancelled entries. The balance sheet reads active entries only. How to confirm: the gap between the two screens equals that opening balance, or the amount of a cancelled entry on that account. What to do: for the financial statements, the balance sheet rules. If your opening entry already includes that account's balance, Bancos counts it twice.
5. The balance sheet says Descuadre de…
Assets stop matching liabilities plus equity when an account with activity has a grouping code that doesn't start with a digit from 1 to 7: the balance sheet can't place it in any section and leaves it out. How to confirm: in the trial balance, find the account with activity that appears in neither the balance sheet nor the income statement. How to fix: correct its grouping code in Configuración → Catálogo de cuentas (Settings → Chart of accounts) (The SAT grouping code); the balance sheet recalculates on its own.