Buyancy
Guide

How Buyancy decides Yes, Wait or No

A fixed calculation over your real bills, paydays and cards decides every answer. An AI model only writes the explanation.

Published Oct 29, 2026 · Checked against the app Oct 29, 2026 · 3 min read

When you ask a what-if, you get a decision you can check. This page explains where the decision comes from, so you can check it.

The decision is a calculation, not a guess

Buyancy looks at your real money and plays the next several weeks forward, one day at a time. It uses:

  • the balance of your checking and savings today;
  • your regular bills, on the days they are due;
  • your payday, on the days you are paid;
  • your credit cards, paid on the day each one is due;
  • the money you put toward your goals;
  • your purchase, on the day you would make it.

Then it looks at the lowest your balance gets, and judges it against your cushion and your minimum balance. That gives Yes, Wait or No.

The same numbers always give the same answer. Nothing in this step is an opinion.

What the AI does, and does not do

Two steps use an AI model, and neither one decides the answer.

  1. Reading your question. The model works out what you are asking: the amount, the date, whether it repeats.
  2. Writing the explanation. Once the calculation has decided, the model puts it into words. It is told the decision and the figures, and it cannot change them.

Your accounts, goals, bills and the people in your household are given to the model as labels like "Account 1", never by name. Your own question is sent as you typed it.

What you see

  • The answer and a short reason. For a Wait, it names the day that is tight and how short you would be.
  • A chart of your checking balance, day by day, with the lowest point marked and your cushion drawn as a line.
  • How to pay. If you have a card, Buyancy judges each way of paying separately, because a card moves the money out of checking on a different day. See paying by card.
  • Every movement, day by day. Open it to see each bill, payday and card payment that went into the chart. If the answer surprises you, this is where to look.
  • What I assumed. The things the answer rests on, such as the date it used for your purchase, each payday it counted, and what it did not count.

When it asks you a question first

If your question leaves something open, like "a flight sometime next month", Buyancy asks once and then goes on with its best guess. It will not ask again. The answer says which parts were guessed.

If your purchase sounds like part of one of your goals, it asks whether you are paying for it from that goal, because that changes the answer.

After a Wait or a No

Buyancy tries a few simple changes and shows the ones that would work:

  • waiting until the day after your next payday;
  • the largest round amount that would still be a Yes;
  • splitting it into two to four equal payments, a month apart.

These are the same calculation with one thing changed. No AI is involved in finding them.

This explains how Buyancy works. It is not financial advice, and it does not know your whole situation.