# Overview

MyBudget is a personal-finance tool for keeping track of where your money is,
where it is going, and whether your spending is on plan. Unlike a spreadsheet
or a simple ledger, MyBudget separates *what actually happened* from *what you
intended to happen*, so you can see at a glance whether reality is keeping up
with the plan.

## The four building blocks

The whole application is built around four concepts. Read them once now —
the rest of this manual just elaborates on them.

Accounts
: Buckets that hold money or track spending. Each account has three independent
  properties — *Transaction or Planning*, *Debit or Credit*, *Frozen or Liquid* —
  which together determine what kind of account it is. See {doc}`accounts` for
  the full table of types.
: **Transaction accounts** mirror something in the real world: a chequing
  account at your bank, a credit card, a mortgage, a term deposit. The balance
  in MyBudget should always agree with the balance the bank sees.
: **Planning accounts** track categories rather than real balances. They show
  the difference between what you planned and what actually happened — for
  example, if you budgeted $1,200 for groceries this month and have spent
  $900 so far, the *Groceries* planning account holds $300.

Transactions
: Real-world events — a salary deposit, a card purchase, a transfer between
  accounts. Every transaction is made up of two or more **splits** and uses
  *double-entry bookkeeping*: every increase in one account is matched by an
  equal decrease somewhere else, so the splits always sum to zero. See
  {doc}`transactions`.

Plans
: Recurring (or one-off) rules that describe what you intend to happen — the
  weekly pay-cheque, monthly rent, the daily interest accruing on a term
  deposit. Plans only ever target *planning* accounts. As real transactions
  flow through the corresponding planning account, its balance shows whether
  you are on track. See {doc}`plans`.

Forecasts
: Projections showing how your cash position will evolve given your current
  plans. Forecasts allow you to make informed decisions beyond your current
  plans, whether that is about immediate unplanned spending or about possible
  changes to them. Forecasts answer questions such as:
  - Can I afford to go out for dinner tonight?
  - When can I afford that new TV?

  Forecasts also show you how well you are positioned to weather any sudden
  unexpected expenses. See {doc}`forecasts`.

:::{figure} ../diagrams/plan-flow.*
:name: fig-plan-flow
:align: center

How the four concepts relate.
:::

## A worked example

Suppose your pay of $4,500 lands in your chequing account on the 1st of every
month. You'd model this as:

* a **transaction account** *Chequing* (Debit, Liquid),
* a **planning account** *Salary* (Income — Debit, Liquid),
* and a monthly **plan** of $4,500 into *Salary*

When the actual paycheck shows up in your bank's CSV export and you import it,
MyBudget records a transaction with two splits: +$4,500 on *Chequing* and
−$4,500 on *Salary*. The plan instalment for *Salary* and the transaction for
*Salary* cancel each other out, so the *Salary* account stays at zero — that
zero is the signal that "reality matched the plan". If your employer were to
short-pay you one month, *Salary* would show a positive balance equal to the
shortfall and you would know straight away that something was off.

Groceries are a softer case: you might budget $1,200 a month but in any given
week spend more or less. The *Groceries* planning account will fluctuate
around zero rather than sitting on it. A small fluctuation is normal; a steady
drift in either direction means the plan needs to be adjusted.

## Getting started

1. Launch the app. From the welcome dialog, **create a new `.mbgt` budget
   file** (or open an existing one).
2. Add your **first transaction account** — typically your everyday chequing
   account. Give it a name and an opening balance dated some time in the past
   (one or two weeks ago is a good default — recent enough that you can find
   the corresponding statement, far enough back that there are some
   transactions to import).
3. **Import transactions** since that opening balance from a CSV export
   downloaded from your bank. See {ref}`csv-import`.
4. **Balance the imported transactions**, creating planning accounts as needed
   to categorise them. See {ref}`balancing`.
5. **Create plans** for your regular income and expenses, attached to the
   planning accounts you just created.
6. Switch to the **Forecasts** tab to see your projected cash position.

You can keep things rolling by importing a fresh CSV every week or two,
balancing the new transactions, and tweaking plans whenever you change your
spending intentions.

## Getting help

This manual is built into the application. **F1** opens it at the page for
whatever you are looking at — press it on the Plans tab and you land on
{doc}`plans`, press it in the *Split Plan* dialog and you land on
{ref}`plan-split`. Dialogs answer F1 themselves, so you do not have to
close one to find out what a field means.

**Help → Contents** does the same thing from the menu bar.