I own a small business and have not paid fica taxes for myself. Does anyone know how I go about making up past taxes? What forms to use?

If you want to pay yourself a salary(salary needs to be reasonable), you can go to the IRS.gov to print out a 941 form each quarter and 940 form for each year, to file the taxes.

You can also file them in your annual federal tax return 1040-SS Self-employment tax return and it will lead you through the calculations.