Three years is the practical minimum. The IRS can audit returns from the past three years under normal circumstances. If they suspect you underreported income by more than 25%, that window extends to six years. Your books should be accurate enough to support the tax returns you’ve filed within those periods.

But tax compliance isn’t the only reason to fix old records. Lenders typically want two to three years of financials when you apply for a business loan. Selling your business? Buyers want three to five years of clean records during due diligence. Bringing on investors? Same story. Think about what you might need the data for before deciding how far back to go.

The older the records, the harder and more expensive they are to reconstruct. Bank statements from five years ago are usually still accessible. But receipts, vendor invoices, and context about what transactions were for? That information fades. Catch-up bookkeeping can categorize historical transactions, but without supporting documentation, some of it becomes educated guessing. Going back more than three years usually means accepting some approximation.

Start with the current year if you have to prioritize. Accurate books going forward matter more than perfect historical records. Once this year is clean, work backward one year at a time based on what you actually need. Trying to fix everything at once often leads to paralysis and nothing getting done.

If your books have never been maintained properly, focus on creating a clean opening balance for January 1 of the current year. This gives you a fresh starting point without having to untangle every transaction from the past decade. Your accountant can work with reasonable opening balances even if the years before that aren’t perfectly reconstructed.

Some situations require going further back despite the difficulty. Ongoing legal disputes might need records from the period in question. State tax audits sometimes have different windows than federal. If you’re in the middle of a dispute or potential audit, talk to your accountant before making decisions about cleanup scope.

The cost of cleanup scales with how far back you go and how messy the records are. One year for a simple business might be a few hundred dollars. Five years of reconstruction for a business with multiple accounts, inventory, and payroll can run into thousands. Get a scope estimate before committing to a full historical cleanup.

A practical approach is to fix the last three years thoroughly, create accurate opening balances, and let anything older stay as-is unless a specific need arises. This covers the audit window, gives you useful trend data, and avoids spending money reconstructing records you’ll never use. Merrimack Valley bookkeepers who specialize in small businesses can help you figure out the right scope for your situation.