Split shared expenses with roommates or a partner using an AI agent

7 min read
Direct answer: Connect the accounts that pay shared bills to an agent with BankBridge, then write your split rules in plain language: which merchants are shared, the percentage each person pays, and which payment-app transfers count as paybacks. Each month, ask the agent to total the shared charges, apply the rules, subtract what was already paid back, and give one number: who owes whom.

1. Write the split rules

Arguments about money between roommates are rarely about the math. They are about rules nobody wrote down. Write them first, in plain language, and agree on them:

Household: me, Sam, Priya

Shared, split equally (1/3 each)
- Electric (merchant contains "CITY POWER")
- Internet (merchant contains "FIBERNET")
- Streaming: the family plan on my card ending 1190

Rent: $2,700 total, I pay the landlord
- Me 40%, Sam 30%, Priya 30% (room sizes)

Groceries: only charges on my card ending 7734 (house card)
- Split equally

Paybacks
- Incoming payment-app transfers from "SAM K" or "PRIYA N" count toward what they owe

Not shared
- Anything else, including takeout, even if ordered for the house

Save the rules where your agent can read them every month: a Claude Project, a file in your Claude Code folder, or a pinned note you paste in.

2. Connect the paying accounts

Connect whichever accounts pay shared bills and receive paybacks at bankbridge.money, then add BankBridge to your agent (Claude, ChatGPT, Claude Code). A dedicated house card makes everything simpler: the rule becomes “everything on this card is shared.”

3. Run the monthly settle-up

On the first of the month:

“Using our split rules, list every shared charge from last month with the merchant, date, amount, and each person's share. Then total what Sam and Priya each owe me. List any charge you were not sure about separately.”

The agent calls list_transactions for the month on the relevant accounts and search_transactionsfor the named merchants, then applies your rules. The “not sure” list is where you add rules: a new streaming service, a hardware store run for the house.

4. Match paybacks

Before sending requests, check what already came in:

“Find incoming transfers from Sam and Priya since the start of last month. Subtract them from what each owes and give me the final balance with a one-line breakdown I can paste into a payment request.”

Incoming transfers show as negative amounts (money in). The agent matches on the sender names from your rules. If someone paid in cash, tell it so it does not ask them twice.

Edge cases worth a rule

  • Mid-month move-ins and move-outs.Prorate by days: “Priya moved in on the 12th; her share of September utilities is 19/30 of a third.”
  • Refunds. A returned grocery item shows as money in on the house card. Tell the agent to net refunds against shared spending in the same month.
  • Annual bills. A yearly membership paid in March can be split in March or spread over 12 months. Pick one and write it down.
  • Pending charges. Settle on posted charges only. Restaurant tips and utility autopays can change before they post.

For couples

Partners often split by income share instead of equally, for example 60/40. Put that in the rules the same way. If you are combining accounts rather than settling monthly, see merging finances with your partner.

Ready? Connect the accounts that pay your shared bills ($5 per month per bank) and run your first settle-up.

FAQ

Does my roommate need a BankBridge account too?

Only if they pay shared bills from their own accounts and you want the agent to see those charges. If you pay everything and they pay you back, connecting your own accounts is enough. Each person's connection only shows the accounts that person linked.

Can the agent request or send the money?

No. BankBridge is read-only. The agent gives you the amount and a short breakdown you can paste into a payment request. You send or request the money in your payment app.

How does the agent know a charge is shared?

From your rules. List the merchants (utility, internet, streaming), the card that is only used for shared spending, or a category like groceries. The agent applies them to each month's transactions and lists anything it is unsure about.

What about uneven splits, like rent by room size?

Write the percentage or fixed amount per person in the rules, for example rent 40/30/30 or internet split equally. The agent applies the right rule per merchant and shows the math line by line so everyone can check it.

Will payment-app paybacks show up?

Yes, as incoming transfers on the account they land in, usually with the app name and often the sender's name in the description. Tell the agent which names to look for and it will subtract those paybacks from what is owed.