I've seen it happen too often: you're a new entrepreneur. You no longer have a paycheck in which mandatory withholdings are calculated for you by your company. Then you get a big surprise on April 15 -- you forgot, or just didn't plan, to save for the IRS bill.
First, it's important to sit down and plan with a tax professional who understands business structures and can advise you on all of your tax liabilities. One in particular, self-employment tax, consists of Social Security and Medicare taxes; if you have set up your company as sole proprietorship (Schedule C) or business partnership, calculating and paying this tax is now completely on you.
If you receive a W-2 through your company, for example under a C-Corp or S-Corp, your company will withhold the proper amount of taxes and remit them to the government on your behalf.
If calculating self-employment taxes are now part of your new job as an entrepreneur, let me make it simple: if your business makes a profit, the IRS will take a cut. Your next step is to estimate this in your cash flow, just like any other expense.
Many new entrepreneurs have no idea how to determine this. For new businesses this can be tricky, because you don't have any historical data to base this on. IRS Form 1040-ES includes a worksheet that can help you calculate your estimated taxes.
During your first year, you may have so many start up costs you may be exempt (because you are operating at a loss). Meet with your tax pro, at least quarterly, to review your financial statement.
Automatic Deposits into Savings
Hopefully, you have decided that separating your business and personal accounts is necessary and you opened a "business only" account. When you set up your business checking account, you should also get a business savings account.
Your next step is to put 30% of your monthly profit (expenses subtracted from your gross income) into this account, ideally early in the month. Self-employment taxes are due on the 15th of April, June, September and January, so every 3 months write that check to the IRS.
If you are following a recommended timely accounting strategy, this will be as simple as looking at the bottom line to calculate your profit for the month. If you are making the same amount of money each month, you can have an automatic transfer each month without having to do any additional calculations. This is the "out of sight, out of mind" strategy, which is as close to mandatory withholdings as you can get when working for yourself.