The IRS has rules regarding the computations and completion of tax returns so that the taxpayer and the preparer have the responsibility to attest to the data.
Every line item on the tax return must have supporting documentation. If you wait until the end of the year to start your bookkeeping, it will be overwhelming. Every business should be keeping up to date records every month
Taxpayers must be willing to to state their figures with the acknowledgement they those figures are true, complete, and accurate.
I can assist you in your bookkeeping, from taking raw receipts and cancelled checks to getting into a reporting format for the completion of your tax return.