Cell Phone and Internet: How Much of the Bill You Can Deduct

Your phone bill has a client call that ran forty minutes long, a text thread with your kid's school, and a group chat that has nothing to do with work, all on one line. The IRS doesn't hand you a deduction for the whole bill just because some of those minutes were business. It hands you a percentage, and that percentage has to hold up if anyone ever asks you to explain it.

Skip this deduction and you leave real money on the table every month. Claim the whole bill and you're setting up a bad conversation with an IRS agent years from now. There's a number in between that's bigger than zero and easy to defend, and finding it takes about ten minutes.

1.The Default Is Zero, Not the Whole Bill

The IRS calls a phone plan or a home internet connection mixed-use property when it serves your business and the rest of your life at the same time. For anything mixed-use, you only get to deduct the share that's actually business. Claim the entire bill, and you're writing off the group chats and the shows you stream after you log off, along with the client calls.

Business expenses have to clear a specific bar under IRC §162: they need to be ordinary and necessary for your work, meaning a cost your kind of business would normally have, not something invented to shrink your tax bill. A phone plan you'd pay for anyway, even if you weren't freelancing, doesn't turn into a full write-off just because you also use it to invoice clients. Only the business-use share does.

Compare that to something like invoicing software or a business insurance policy. Nobody buys those for personal reasons, so the entire cost is a business expense with no split required. A phone and an internet connection sit in a different category, because a version of both would exist in your life even if you'd never taken on a single client.

2.A Second Line Skips the Math Entirely

IRS Publication 587 draws this line clearly for landlines. The base cost of the first phone line into your home is a personal expense, full stop. A second line installed and used only for business is a separate deductible expense, the whole cost of it, reported on Schedule C line 25 instead of folded into your home office numbers.

The IRS hasn't written a cell-phone version of that same rule, but tax preparers apply the identical logic. Add a second cell plan used only for client calls, invoicing, and business texts, and the entire bill for that line is deductible. Skip the extra line and keep one phone for everything, and you're back to splitting a single bill by percentage.

3.Figuring Your Percentage Without Guessing

If you're sticking with one phone and one internet connection for both business and life, you need a business-use percentage you can show your work on. A few ways to get there:

• Call log method. Pull one or two recent months of call and data logs from your carrier's app, count what's client related, and apply that share to the full year.
• Work-hours method. If your phone stays on your desk during set work hours and off to the side the rest of the day, the share of your waking day spent working is a reasonable stand-in for business use.
• Router dashboard method. Some home routers show which hours of the day see the most traffic. Cross-reference that against your work schedule to estimate how much of your internet use lines up with business hours.

None of these have to be precise to the minute. They have to be consistent, written down, and something you'd feel fine repeating out loud to an IRS agent.

Redo the estimate when your work actually changes, not every single year out of habit. Pick up a second client who calls constantly, or move your whole workflow onto video calls that eat your data plan, and your old percentage stops matching reality. Keep the old year's math on file next to the new one, so you can show why the number moved if anyone asks.

4.Where Each Setup Lands on Your Return

The setup you choose changes both the deduction and where it goes:

That last row surprises people who already claim the home office deduction. Your home office percentage is based on square footage, and it exists to split space-based costs like rent and utilities. Internet isn't a space-based cost. Most tax preparers calculate its business-use share on its own, using how you actually use the connection, not how big your office is relative to your home.

The same table applies whether you run as a sole proprietor or a single-member LLC. The business structure changes how you're taxed overall, not whether a phone bill counts as mixed-use property. Schedule C looks the same either way, and so does the math behind it.

5.What Happens If You Claim 100%

Say your phone bill runs $85 a month and you land on 60% business use after reviewing your call logs. That's $51 a month, or $612 for the year. Add a $70 internet bill at 40% business use, another $28 a month, and you're at $336 for the year. Combined, that's $948 you can defend on your Schedule C.

Claim 100% on either bill instead, and you're telling the IRS you never once used your phone or your internet connection for anything personal, all year. Most tax preparers flag that figure as one of the first things an examiner questions, because almost nobody's actual usage looks like that.

Keep a copy of the bill or the call log you used to calculate the percentage, along with a short note explaining the method. A screenshot of a carrier app pulled once a year takes thirty seconds and is worth more than a confident guess if that year's return ever gets a second look.

6.A Percentage You Can Actually Defend

Adam Smith, the economist whose 1776 book The Wealth of Nations laid out the founding principles of modern taxation, wrote that a tax ought to be certain, not arbitrary, with the amount owed clear and plain to the person paying it rather than left to guesswork.

"The tax which each individual is bound to pay ought to be certain, and not arbitrary."

The same standard works in reverse for a deduction. Your business-use percentage should be a number you arrived at on purpose, from call logs or a work schedule or a router dashboard, not a round figure you picked because it sounded reasonable. Write down how you got the number the same year you use it. Five years later, when the memory of which calls were business and which weren't has faded, that note is the only thing standing between you and a guess.

If you want a full pass over every recurring bill like this one, not just phone and internet, the free check at simplance.org/profit-audit walks through your numbers against what's typical for similar freelance work.

A phone and internet deduction this small rarely gets its own line of attention on a return. It should. Sixty seconds a month logging which calls were client work adds up to a deduction you can actually keep, built on a number you can explain instead of one you hope nobody asks about.

Multiply $948 by five years of the same habit and you're looking at close to $4,740 in deductions built on nothing more than a monthly habit and a short note explaining how you got there. That's a return worth a lot more than the ten minutes a year it costs you.