Brent Walther

Personal Finance with GnuCash

Saturday, May 30, 2020

Background

Shortly after I graduated from college and began my career, I became more interested in personal finance and wanted to be more hands-on with the management of all of my finances (more thoughts can be found in Personal Finance Philosophy). I wanted to be able to see all of my finances in one place, run reports (budget, cash flow, and net worth reports mostly), and feel like I knew exactly where money was coming from and going. I stumbled across double entry accounting and the free and open-source accounting program GnuCash and knew it would allow me to build the complete picture that I desired. I just needed to learn how to use it.

What is double entry accounting?

Double entry accounting may have confusing online definitions for somebody who’s never studied it in school, but it essentially boils down to a simple principle: any money that flows to or from an account you come from or go to some other account (it’s entered twice (double entry) - once in each account). Some simple examples:

There are five types of accounts: Income, Expense, Asset, Liability, and Equity. For the purposes of personal finance, the first 4 are the most interesting. All transactions are ‘split’ between 2 of these accounts (sometimes more, but that’s getting advanced) and recorded in a ‘ledger’. The cash ‘flows’ from one to the other. Here’s a simple example where every dollar amount is a split that’s recorded in the ledger:

Simple example image of double-entry accounting.
There are 5 transactions in this example.

The accompanyin ledger (if you were looking at all accounts at once) would look like the below table. Note that the balance is the running balance for each individual account, not a total running balance. I use parantheses to represent negative balances:

Date Description Account Amount Balance
2020-05-07 Paycheck Income>Salary -$1000 ($1000)
2020-05-07 Paycheck Assets>Checking Account +$1000 $1000
2020-05-14 Walmart Liability>Credit Card -$200 ($200)
2020-05-14 Walmart Expenses>Groceries +$200 $200
2020-05-16 Tex-Mex Food Liability>Credit Card -$100 ($300)
2020-05-16 Tex-Mex Food Expenses>Restaurants +$100 $100
2020-05-21 Paycheck Income>Salary -$1000 ($2000)
2020-05-21 Paycheck Assets>Checking Account +$1000 $2000
2020-05-31 Rent Assets>Checking Account -$1300 $700
2020-05-31 Rent Expenses>Rent +$1300 $1300
2020-05-31 Pay CC Assets>Checking Account -$300 $400
2020-05-31 Pay CC Liability>Credit Card +$300 $0

The ledger becomes a simple database. To see if you’ve fully reconciled the account and recorded all the transactions, you can simply compare the balance in your ledger with whatever your actual balance is online. They should be equal if you’ve reconciled all transactions.

GnuCash

GnuCash is simply an accounting tool that allows you to do double-entry accounting just like above with accounts that you set up. You can enter transactions manually (which is tedious but fine if there are few to catch up) or you can import them using CSV or OFX files (most banks and credit card companies have “download transactions” buttons for one or both of these formats). The main screen is an account overview that shows the overall balance of every acccount and you can dig in to the individual ledger for each account to look at the transactions for it.

Setup

The biggest hurdle when setting up GnuCash is understanding what accounts you need to set up. It can seem like a lot to manage at first, but you’ll realize quickly that most of the accounts are the expense categories you want to track in your budget. When I started, these were the accounts I started with:

Note that I only had a few physical accounts:

  1. An Ally checking and savings account.
  2. A 401k and Roth IRA with Vanguard
  3. A credit card with Capital One
  4. A credit card with Chase
  5. A student loan account

To get started, you essentially need to add all the accounts you want to track and then balance them all up. To do this in the very beginning, I just used transferred money to/from the “Equity>Opening Balance” account to all the physical accounts so that the balances matched what they showed online. This balancing step where you transfer money from to open the balance is something you only ever do once when you set everything up. From then on, you only track transactions that appear in the accounts.

Updating the ledger

Normally I update the ledger once a month. Usually, I’ll do it in the first few days of the month and import/reconcile all the transactions from the previous month for each account. I’ll usually do the following:

  1. Log in to Ally and enter the transactions from the month manually. I don’t normally use my debit card to make any purchases so the number of transactions is usually limited to paychecks, interest, rent, and credit card payments. The transfers either come from an Income account or go to a Liability or Expense account directly.
  2. Log on to Vanguard and add any new investment purchases that came from my payroll. Since payroll deductions never actually enter your bank account, this money transfers from an “Income:Retirement” account. Since investments grow, the balance will not always match what you have in GnuCash. After practicing this accounting workflow for a hile, I began doing reconcile balance transfers from an “Income>Unrealized Capital Gains” account.
  3. Log on to each credit card and download all the transactions as a CSV or OFX and import them using the GnuCash import tool. Sometimes it matches them to expense accounts automatically (though my main complaint with GnuCash is how crappy the auto-matcher is). Un-matched expenses get matched to the “Imbalance-USD” account automatically and you just need to change the transfer account to an Expense account for each transaction.
  4. Cross-check all the balances of my physical accounts with what GnuCash says to make sure they’re up-to-date and I didn’t miss any transactions.
  5. Done!

Reports

GnuCash has some reasonably rich reports for your accounts. In particular, the Expenses report can break down all your expenses categories by month and show you where all your money is going. Usually I would take the data from this report and put it in a Google Sheets spreadsheet to make more interesting graphs or format it exactly how I wanted it. I’d also run a Net Worth report and break down the Asset and Liability categories to see how I was saving. Ideally your Net Worth should grow over time as you save.

I looked at the Cash Flow reports for a little bit too (but don’t regularly consult them) to see a precises picture of how much of my income was actually getting spent. Ideally your cash flow is always in the green which means you spent less than you earned. That green should go into the appropriate savings bucket per your own personal philosophy and financial position.

Getting tired of GnuCash

While GnuCash is a powerful tool, I eventually got to the point where the bottleneck of the entire workflow was the crappy transaction matcher. Even with a couple thousand transactions examples in the database, it still failed to auto-match many transactions which took time to do manually. I began working on an auto-matching tool that could do a better. It was easy enough to read the GnuCash database but making it fully interoperable with GnuCash was not worth the time. I eventually found the ledger-cli tool that does pretty much everything I use GnuCash for but uses a simpler text file format that allows you to write scripts for it much easier.