Prep your mortgage application with an AI agent: large deposits, overdrafts, and recurring debts

What underwriters look for

When you apply for a mortgage, the lender asks for recent bank statements, usually the last two months for each account holding your down payment and reserves. An underwriter reads them to confirm the money is yours and has been yours, and to look for obligations that are not on your credit report. Common questions:

• Where did this large deposit come from?
• Why are there overdraft or returned-payment fees?
• What is this recurring payment to a person or company?
• Why does your balance drop sharply on a certain date?

Each question can mean a letter of explanation plus documents, and requests that arrive late in the process can delay closing. Finding them yourself a few weeks early gives you time to gather paperwork.

Find deposits you will need to source

Connect the accounts you will submit (see connecting multiple banks). Work out your threshold with your loan officer. For conventional purchase loans, Fannie Mae's guidance uses 50% of total monthly qualifying income; some lenders go lower. Then ask:

“List every deposit over $2,000 in the last 90 days across my checking and savings accounts that is not my regular payroll. For each, show the date, account, amount, and description. Also flag any cash deposits of any size.”

The agent uses list_transactionswith a date range and amount filter. Remember that deposits come back as negative amounts (money in) and charges as positive. A good agent handles that, but if the list looks empty, say “deposits are negative amounts.”

For each deposit, write down where the documentation lives: a gift letter and the giver's statement, a bill of sale, a tax refund notice, a transfer from another of your accounts (which means that account's statement too).

Find overdrafts and returned items

“Search the last six months for overdraft, NSF, insufficient funds, or returned item fees. List them with dates.”

The agent runs search_transactions for each term. One overdraft with a reason is usually a short explanation. A pattern is worth knowing about before you apply.

List recurring payments

“List my recurring charges and recurring transfers out. Mark any that look like loan payments, payment plans, or payments to individuals.”

get_recurring_charges finds repeating payments by merchant and cadence. Underwriters compare these against your credit report. A private loan, a buy-now-pay-later plan, or a regular payment to a person may need an explanation or count toward your debt-to-income ratio. Better to raise it with your loan officer than have it found.

Draft letters of explanation

A letter of explanation is short: what happened, why, and the supporting document. Ask:

“For each deposit and fee you flagged, draft a two-to-three sentence explanation with a placeholder for what I will attach. Use only facts from the transactions; leave blanks where I need to fill in a reason.”

Edit every draft. The agent knows the amount and date, not the story. In Claude Code, have it write the drafts to a file so you can send them to your loan officer when asked.