Track 2 · Real-Life Money → Phase 11: Taxes, A Bit Deeper
Side income & 1099s — what you owe
Side income is taxable from the first dollar, nobody withholds for you, and self-employment tax adds 15.3% on top of income tax — which is why you set aside 25–30% of every side-gig dollar the day it lands.
The situation
Our $48,000 first-jobber picks up a weekend side gig — freelance design, about $3,000 a year after expenses. The money arrives whole: no withholding line, no FICA line, just the full payment. It feels like the cleanest money they’ve ever made. Lesson 2.5 already whispered the catch: it only looks clean because nobody has collected the taxes yet.
The idea
Three things about side income are durably true, no matter how this year’s forms and thresholds shake out:
1. It’s taxable from the first dollar. There is no “under some amount is free” rule. Cash, app payouts, marketplace profits, freelance checks — income is income, form or no form.
2. Nobody withholds for you — and you’re both employer and employee now. A W-2 job withholds as you go and pays the matching half of your FICA (lessons 2.1 and 2.3). A side gig does neither. So you owe self-employment tax: 15.3% — that’s 12.4% Social Security + 2.9% Medicare, both halves, as lesson 2.5 explained — applied to 92.35% of your net self-employment earnings (the IRS taxes slightly less than 100% to mirror what employees experience). It’s owed once your net earnings reach $400 for the year. And that’s just the FICA replacement — regular income tax applies on top.
3. The IRS expects to be paid during the year, not just in April. If you’ll owe $1,000 or more for the year beyond what your day-job withholding covers, you’re generally expected to make quarterly estimated payments. A practical shortcut for someone with a W-2 job: raise the withholding on your paycheck (lesson 2.4’s W-4) to cover the side-gig tax instead.
About the form you’ve probably heard arguing about online: payment apps and marketplaces may send you (and the IRS) a 1099-K reporting what you were paid — but the dollar threshold for when they must has changed repeatedly, so check irs.gov for the current rule. It doesn’t change a thing about what you owe: taxable from dollar one, with or without paperwork.
The rule of thumb: set aside 25–30% of every side-gig dollar the day it arrives.
By the numbers
Run the anchor’s $3,000 side gig through the actual machine:
| Step | Amount |
|---|---|
| Net side-gig earnings | $3,000.00 |
| × 92.35% (the slice SE tax applies to) | $2,770.50 |
| × 15.3% self-employment tax | ≈ $424 |
So about $424 of self-employment tax — before any income tax. At the anchor’s 12% marginal rate, regular income tax adds roughly $335 more (you get to deduct half the SE tax automatically, so it’s a bit under 12% of the full $3,000).
Total: about $760 on $3,000 of side income — almost exactly 25%. That’s where the set-aside rule comes from. It isn’t caution; it’s arithmetic. The 25–30% sitting in that separate savings account in April is the difference between “filing took an afternoon” and “I owe WHAT?”
Where this fits
Same playbook as lesson 2.5, now with the real machinery: dollar one taxable, 15.3% on 92.35%, $400 floor, $1,000 quarterly trigger, 25–30% set aside. Next lesson flips from what you owe to what you can shelter — the recap of every legal tax break you’ve collected across this course.
Do it
If you have any side income this year, set up the habit today: open (or designate) a separate savings account and move 25–30% of every side-gig payment into it the day it arrives. That money is taxes — it was never yours to spend.
Check yourself
1. From which dollar of side income do you owe tax?
Income is income. Whether a form arrives or not, side earnings are taxable from dollar one — the durable rule that never changes, no matter how reporting thresholds move. ($600 is an old form-reporting threshold, not a tax-free floor.)
2. Why is self-employment tax 15.3% when a W-2 employee only sees 7.65% taken out?
A W-2 employer quietly pays the matching 7.65% for you (lesson 2.3). Self-employed, both halves are yours: 12.4% Social Security + 2.9% Medicare = 15.3% — and income tax is still on top of that.
3. On $3,000 of net side income, the self-employment tax is about:
SE tax applies to 92.35% of net earnings: $3,000 × 92.35% = $2,770.50, then × 15.3% ≈ $424. Both halves are yours, so it's the full 15.3%, not 7.65%.
4. When are quarterly estimated tax payments generally required?
The IRS expects to be paid as you earn, not just in April. The general trigger is expecting to owe $1,000+ for the year — though raising the withholding at your day job can cover the gap instead.
5. A payment app never sends you a 1099-K for your side income. What do you owe?
Forms are reporting paperwork, not permission slips. The threshold for when apps must send a 1099-K has changed repeatedly — your obligation never did.
Keep this
Side income is taxable from the first dollar. Self-employment tax is 15.3% on 92.35% of net earnings (owed once you net $400+ for the year), plus regular income tax on top — set aside 25–30%, and pay quarterly estimates if you'll owe $1,000 or more.