The settings that change your numbers

Most settings are cosmetic. These four, all on Settings → Business, actually change what your reports and tax worksheet say. Each is set once, sensibly defaulted, and worth two minutes of understanding.

Your time zone

Reports count a day from midnight where you are. Get this wrong and, as the app itself warns, a payment taken on the evening of December 31 can land in the wrong tax year. Thalermark asks for the time zone during setup and offers a one-click fix if your browser ever looks like it’s somewhere else. Check it once; it matters most at year-end.

When you count income

This is about timing: which year a payment counts for.

When you get paid (the default, and the usual choice for freelancers and trades): an invoice you sent in December but got paid for in January counts as January’s income.
When you send the invoice: that same invoice counts as December’s income, even though the money arrived later.

Only change this if whoever does your taxes tells you to. As the app puts it, switching is a bigger deal with the IRS than it looks. The tax worksheet lets you view your year either way without changing the saved setting, and says so when the view and the setting disagree.

Big purchases, first year

When you spread a big purchase’s cost over years, this decides how much counts in year one:

Half the usual amount (the default): a $3,600 mower over five years counts about $360 the year you buy it, then about $720 a year after that.
The full amount: that same mower counts about $720 every year, starting the year you buy it.

Vehicle costs

The IRS lets you deduct business driving one of two ways, and you pick one:

A flat rate for every business mile (the default, and the better fit for most trades): log your trips and Thalermark works out what they’re worth. The rate already covers gas, repairs, insurance, and the vehicle’s wear, so don’t also claim those as expenses.
What the vehicle actually cost me: your real gas, repairs, and insurance, scaled to the share of your driving that was business. Thalermark can’t total that for you, so your mileage log becomes a record only, and that tax line is yours to fill in.

Also on this tab: how your business is set up

Sole proprietor, LLC, partnership, S-corp, C-corp. It drives which tax form your worksheet mirrors. If you change it, Thalermark asks the one question that matters: did you register a new business with its own EIN? Same business, and your categories just update; new EIN, and it walks you through setting up the new business properly.