Budgets on a per-account basis can be added via custom directives in the Beancount file:

2012-01-01 custom "budget" Expenses:Coffee       "daily"         4.00 EUR
2013-01-01 custom "budget" Expenses:Books        "weekly"       20.00 EUR
2014-02-10 custom "budget" Expenses:Groceries    "monthly"      40.00 EUR
2015-05-01 custom "budget" Expenses:Electricity  "quarterly"    85.00 EUR
2016-06-01 custom "budget" Expenses:Holiday      "yearly"     2500.00 EUR

If budgets are specified, Fava's reports and charts will display remaining budgets and related information.

The budget directives can be specified daily, weekly, monthly, quarterly and yearly. The specified budget is valid until another budget directive for the account is specified. The budget is broken down to a daily budget, and summed up for a range of dates as needed.

This makes the budgets very flexible, allowing for a monthly budget, being taken over by a weekly budget, and so on.

Fava displays budgets in both charts and reports. You can find a visualization of the global budget in the Net Profit and Expenses charts for the Income Statement report.

The Expenses Income Statement report is a good starting point for getting access to the full budget information in Fava. The Changes charts visualize the data. The Changes (monthly) and Balances (monthly) reports show, respectively, the monthly and cumulative (over the selected period) budgets.