When you are self-employed, you are required to keep accurate and reliable business records, and to report all your income and expenses, even if you don't get tax forms from your clients or customers. Keep your records for at least 3 years from the date you file. If audited, the IRS can inspect your bank account to find income you didn't report, and they don't have to give you credit for any expense deduction you can't prove.
You will also likely owe quarterly payment of estimated income taxes, and you may be penalized if you did not make timely payments. If this is your first time owing a penalty, you can request a one-time penalty waiver (abatement) after you get your penalty notice.
