Bookkeeping is something that should be done contemporaneously or “as you go.” It can be done manually on paper or using software such as spreadsheets or bookkeeping software.
You should keep copies of all business records including receipts. They can be paper receipts or online records including images of paper receipts. Cancelled checks or credit card statements alone may not be sufficient. The records should include the specific product or services.
Since your business is an LLC, you should maintain separate accounts (e.g., checking and savings) for your business. You should not commingle business and personal accounts.
In general, you normally would not need to pay taxes if you did not have a profit. However, some states require payment of an annual tax for registered businesses such as LLCs.
Here’s a link about keeping tax records: https://turbotax.intuit.com/tax-tips/tax-planning-and-checklists/keeping-good-tax-records/L61fGcXtc
