YNAB Multi-Budget FX Sync Tool

Note: this is mostly vibe-coded, but was reviewed and works for me. Use at your own risk.

Sync transactions between two YNAB budgets with automatic currency conversion.

Use Case

• You have a destination YNAB budget where you manage most of your finances
• You have a source budget in a different currency with fewer transactions
• You want to sync transactions from the source budget to your destination one, converting amounts while preserving payees and categories

Installation

Requires Python 3.10+.

# Using uv
uv run ynab-multi-budget-fx.py

# Or install dependencies manually
pip install ynab rich questionary httpx
python ynab-multi-budget-fx.py

Configuration

On first run, you'll be prompted for:

1. YNAB API Key - Get one from YNAB Developer Settings
2. Destination budget - Target budget (receives synced transactions)
3. Source budget - Budget to sync transactions from
4. Cutoff date - Only sync transactions since this date

Configuration is cached in ~/.local/share/ynab-multi-budget-fx/config.json.

Data Storage

All data is stored in ~/.local/share/ynab-multi-budget-fx/:

• config.json - Budget IDs, API key, cutoff date, adjustment category
• rates_cache.json - Cached FX rates (keyed by base:target:date)
• currency_data.json - ISO 4217 currency symbols for memo formatting

How It Works

1. Validation - Maps categories and accounts between budgets by name. Source budget must have a subset of the categories and accounts of the destination budget.

2. Transaction sync - Fetches transactions from the source budget since the cutoff date. For each new transaction:

   • Converts the amount using daily FX rates
   • Maps category and account IDs to the destination budget
   • Appends FX info to memo (e.g., 100.00€ @1.05 or 100.00 EUR @1.05)
   • Sets import_id to MB:<orig_tx_id> to track synced transactions

3. Transaction updates - Previously synced transactions are detected via import_id and updated if the source transaction's amount or memo has changed.

4. Balance adjustments - After syncing, compares account balances and offers to create adjustment transactions for any discrepancies (only for differences ≥1 in target currency).

Special Cases

• Transactions with payee <IGNORE> are skipped
• Split transactions are fully supported
• Synced transactions are created as unapproved for review

FX Data

Uses the Exchange API for historical exchange rates.

• Rates are fetched in parallel and cached locally to avoid redundant API calls
• If a rate is unavailable for a specific date, automatically falls back to the previous day
• Multiple CDN endpoints are tried for reliability

Dependencies

• ynab - Official YNAB API client
• rich - Terminal formatting
• questionary - Interactive prompts
• httpx - HTTP client for FX API