Build YNAB

The build, in order

1. 1

   Accounts and transactions

   hideshow

   Fast keyboard entry, balances computed by query, cents stored exactly.

   1. 1.1Create the project and the tables

      accounts (id, name, kind, on_budget, closed), category_groups, categories, budgets (month, category_id, assigned_cents), transactions (id, account_id, date, payee, category_id, amount_cents signed, memo, cleared, reconciled, transfer_transaction_id), payee_rules.

      terminalcopy

      mkdir budget && cd budget && git init && npm init -y && npm pkg set type=module
      npm install express@4 better-sqlite3@13
      mkdir data && cp .env.example .env

   2. 1.2Build account CRUD and the transaction entry form

      Keyboard-first: date, payee, category, amount, memo, enter to save. Parse 12.10 into 1210; never store a float.

   3. 1.3Compute balances by query, not stored

      A cached balance drifts and you cannot tell which number lies.

   done when · tick each as it passes

   • Ten transactions across two accounts yield balances matching a hand sum
   • Editing an amount updates the balance; deleting restores it
   • Entering 12.10 stores 1210 and renders $12.10 exactly

   next phase
2. 2

   Categories and the budget grid

   hideshow

   Assigned, activity and available per category per month, with rollover.

   1. 2.1Build groups and categories from your list
   2. 2.2Build the monthly grid

      activity = sum of the category's transactions that month; available = last month's available + assigned + activity.

   done when · tick each as it passes

   • Assign $200 to Groceries, spend $50: assigned 200, activity -50, available 150
   • Next month opens with 150 available before anything is assigned
   • An overspent -20 carries into the next month rather than resetting

   next phase
3. 3

   To Be Budgeted

   hideshow

   The header number the whole method rests on.

   1. 3.1Compute inflow to on-budget accounts minus everything assigned across all months

      One query; reconcile it against a hand calculation on a fixture.

   2. 3.2Show it in the header on every budget page, red when negative

      This number is the entire method: every dollar has a job, and the app's job is to tell you when one does not.

   done when · tick each as it passes

   • Adding $1,000 income raises it by exactly 1000
   • Assigning $400 lowers it by 400
   • Over-assigning turns it red with the correct negative figure

   next phase
4. 4

   CSV import

   hideshow

   Import any bank's CSV once you have mapped it, dedupe, and learn payees.

   1. 4.1Build the column-mapping step per account

      Date, payee, amount or debit/credit columns. Ask the date format once and store it; never guess between DD/MM and MM/DD.

   2. 4.2Dedupe on date, amount and payee and preview what will be skipped
   3. 4.3Apply payee_rules and learn a rule when you categorize a new payee

   done when · tick each as it passes

   • Importing the same file twice adds nothing the second time
   • An ambiguous date format is asked about rather than assumed
   • A credit-card CSV with inverted signs imports with correct polarity
   • A known payee arrives pre-categorized

   next phase
5. 5

   Reconciliation

   hideshow

   Match the bank to the cent and lock what matched.

   1. 5.1Build the reconcile flow

      Enter the real balance, see the difference against cleared, tick transactions cleared until zero, lock them reconciled.

   2. 5.2Offer a balance adjustment transaction for a remaining difference

      An auditable row rather than a silent edit of history.

   done when · tick each as it passes

   • A $3 discrepancy is reported precisely
   • Ticking the missing transaction clears it
   • Reconciled transactions resist accidental edits
   • The adjustment path leaves an auditable row

   next phase
6. 6

   Credit cards

   hideshow

   Spending on a card moves the assigned money to the card's payment category.

   1. 6.1Implement the credit-card payment category rule

      A categorized purchase on a card reduces that category's available and raises the card's payment category by the same amount.

   2. 6.2Treat paying the card as a transfer that reduces both

      Show the payment category in the grid so the money set aside for the bill is visible.

   done when · tick each as it passes

   • A $50 grocery purchase on a card reduces Groceries by 50 and raises the card payment category by 50
   • Paying the card as a transfer reduces both correctly

   next phase
7. 7

   Reports and backups

   hideshow

   Spending by category and net worth, and a backup you have restored.

   1. 7.1Build the two reports as inline SVG
   2. 7.2Nightly copy of the database to backups/, thirty kept, and one restore performed
      terminalcopy

      sqlite3 data/budget.db ".backup 'backups/budget-$(date +%F).db'"

   done when · tick each as it passes

   • Report totals match the transaction table
   • A restore has been performed once

   next phase
8. 8

   Optional bank sync, honestly priced

   hideshow

   SimpleFIN behind an interface, with CSV as the other implementation and no bank credentials in your app.

   1. 8.1Exchange the setup token for the access URL once
      terminalcopy

      curl -s $(echo $SETUP_TOKEN | base64 -d)  # the decoded setup token is a claim URL; POST to it once to receive the access URL

   2. 8.2Implement the sync source

      GET the access URL's /accounts, map transactions to your model, dedupe against manual entries by date, amount and payee.

   done when · tick each as it passes

   • A sync pulls new transactions and dedupes against manual entries
   • The app works completely with sync disabled and no token present

   next phase