The IRS probably already has your bank information due to its ability to dig. How does the IRS know about your finances? There is one simple answer, a substantial paperwork trail. I have provided some examples below.
Your previously filed tax statements (W-2,1099, etc) were completed under your social security number. This information is then collaborated with the social security administration to give them a good faith estimate of your current income.
If you earned more than $10 of interest in a year through a bank, the bank has to file a 1099-INT.
Investment accounts which include dividend transactions and stock sales will be reported through the forms of 1099-DIV and 1099-B.
If you own an IRA, those are reported through Form 5498.
If you are an online seller, merchant accounts which meet a minimum number of transactions for the year will have a trail of 1099-K forms.
The IRS also has a team of revenue officers and revenue agents whose jobs are to examine whether or not all of your income is reported. These individuals also have the power to request financial records from you. If you refuse to provide these records, they may summon these from your financial institutions.
In the case of most summons, it is highly recommended that individuals immediately consult a tax professional such as myself or an enrolled agent.