New Bookkeeping Client Onboarding Checklist: Every Document to Collect on Day One

Every bookkeeper has lived some version of this story. You take on a new client, get the books "mostly" set up, and three months later you find a business credit card nobody mentioned, with thousands in charges that never touched the ledger. Now you're re-reconciling a quarter you thought was closed.

A good bookkeeping client onboarding checklist exists to prevent exactly that. The goal on day one is to collect everything you need to reconstruct a complete, accurate picture of the business before you touch a single transaction. What follows is the full document list, grouped by category, with why each item matters and the downstream mess when it gets skipped.

Why bookkeeping client intake deserves a real system

The information you gather during intake sets the ceiling on how accurate the books can ever be. You can't reconcile an account you don't know exists, or categorize a loan payment you've never seen the agreement for. Onboarding is the one moment when the client is motivated to hand you things, so ask for all of it while that window is open. Two weeks in, their attention is gone and every follow-up email takes a week to answer.

Treat the checklist below as the master list. Not every client will have every item, but mark each one "collected" or "confirmed does not apply." Anything ambiguous is a future surprise.

Entity and formation documents

Start with who and what the business legally is.

• Formation documents (Articles of Incorporation or Organization, partnership agreement, operating agreement)
• EIN confirmation letter (IRS CP-575 or a 147C replacement)
• S-corp election confirmation (Form 2553 acceptance) if they elected S-corp status
• DBA / fictitious business name filings

Why it matters: Entity type drives everything downstream: how owner pay is handled, whether there's payroll, how equity is tracked, which tax return gets filed. An S-corp owner who thinks they can take random "draws" is a problem you want to catch in week one, not at tax time. Miss it and you build an equity structure that doesn't match reality, or discover mid-year that the "LLC" is actually taxed as an S-corp with a reasonable-salary requirement nobody planned for.

Prior-year tax returns

Get the last filed business return, and the year before too if the business is more than a couple years old.

Why it matters: The tax return is your Rosetta Stone. It tells you the ending balances the previous preparer relied on, what depreciation schedules are in play, whether there are carryforwards, and how the entity actually files. Your opening balances should tie to it. Skip it and your beginning balances float free of anything the IRS has on record, so come tax season the CPA finds your retained earnings and fixed assets don't match the prior return and you're doing forensic cleanup to explain the gap.

Chart of accounts and prior bookkeeping file

You need access to whatever came before you, even if it's a mess, especially if it's a mess.

• Existing accounting file (QuickBooks Online transfer, a desktop backup, Xero access, or the spreadsheet they've been keeping)
• Current chart of accounts
• The most recent reconciled balance sheet and P&L
• The date through which the books were last reconciled (get this in writing)

Why it matters: You're either continuing existing books or rebuilding them, and either way you need the starting point and the history. The "last reconciled through" date tells you where clean records end and your cleanup begins. Skip it and you build on unreconciled garbage or duplicate months already done, both of which cost hours you can't bill cleanly.

Every bank and credit card account (and how to make sure none are missed)

This is the category that bites people, so give it extra attention.

• Every business checking and savings account (bank name, last four, statement access)
• Every business credit card
• PayPal, Stripe, Square, and other processor balances that function like accounts
• Any personal account used for business (common with sole props and new LLCs)

How to make sure none are missed: Don't just ask "what are your accounts?" People forget the card they use for one vendor. Cross-check instead: pull the prior-year return for interest income and expense (which point to accounts), and scan the main checking account for transfers and card payments. The forgotten account almost always surfaces in the transfer trail.

When it's skipped: You find the account in month three, as in the opening story, and re-open a closed period. If it's an income account, the business under-reported revenue, which is a tax problem, not just a bookkeeping one.

Loan and financing agreements

• Loan agreements and amortization schedules for term loans, SBA loans, and equipment financing
• Lines of credit
• Vehicle and equipment leases
• Any owner or related-party loans

Why it matters: Every loan payment splits between principal and interest. Without the amortization schedule you're guessing, and guessing wrong misstates both the liability and the expense. Related-party loans especially need documentation so they aren't misread as income or distributions. Skip it and the full payment gets dumped to "loan expense," the liability never moves, and the interest deduction is wrong.

Payroll setup

• Payroll provider access (Gusto, ADP, QuickBooks Payroll, etc.)
• Recent payroll reports and the most recent quarterly filings (941s, state equivalents)
• List of employees vs. contractors
• W-9s on file for contractors

Why it matters: Record payroll from the bank feed without the provider's reports and you'll never split wages, taxes, and fees correctly. The employee-vs-contractor distinction also flags worker-classification risk you'll want to raise early. Skip it and payroll tax liabilities sit uncategorized, filings don't tie to the books, and 1099 season becomes a scramble because no one collected W-9s.

Sales tax and merchant accounts

• Sales tax registration and filing frequency for each state where they collect
• Recent sales tax returns
• Merchant processor accounts and their fee/deposit structure

Why it matters: Merchant deposits are almost always net of fees, so what hits the bank is smaller than the sale. Record the deposit as revenue and you understate both income and processing expense. Sales tax collected is a liability, not revenue, and misreading it inflates the P&L while a real obligation quietly builds with no one watching the deadlines.

Software logins and accountant access

• Accountant/advisor access to the accounting platform (not the owner's personal login)
• Read access to bank and card portals where practical
• Access to expense, invoicing, inventory, or POS tools in the stack
• A list of recurring vendors and subscriptions

Why it matters: You can't do the work you can't get into, and accountant-level access keeps you auditable instead of logging in as the owner. Skip it and you're blocked constantly, waiting on the client to pull reports you should be able to pull yourself, and every close slips.

A tool like BookkeeperCollect turns this checklist into a branded upload portal you send once, so the client sees every item, uploads as they go, and you stop chasing documents by email.

Sequencing: what you need and when

Not everything is needed at the same moment, and collecting in the wrong order stalls the engagement.

Before the engagement letter, you need enough to scope and price accurately: entity type, rough transaction volume, number of accounts, and whether there's payroll and sales tax. Under-scoping here is how you end up doing a cleanup-sized job for a monthly-maintenance fee.

After signing but before you start work, collect the bulk documents and access: bank and card statements, prior-year return, loan agreements, payroll and platform access.

Before the first monthly close, confirm you have complete statements for every account, all opening balances tie to the prior return, and every account is on the bank feed. The first close is where gaps become obvious, so finish the intake list before you get there.

Red flags to watch for during onboarding

• "I'm not sure how many accounts we have." Expect at least one you haven't been told about. Do the transfer cross-check.
• Books that were "reconciled" but the balance sheet has negative cash or a stale, never-changing loan balance. They weren't reconciled.
• Reluctance to grant accountant-level access. Sometimes a control issue, sometimes hiding a mess. Either way, name it early.
• No prior-year return "because we just switched preparers." Get it before you commit to opening balances.
• Commingled personal and business spending with no clear line. Fixable, but it changes your scope and cleanup estimate.

How long onboarding should realistically take

For a small, clean client with one or two accounts and no payroll, onboarding can wrap in a week or two once documents come in. The bottleneck is almost never your work; it's how fast the client sends things, which is exactly why a single clear request beats a slow trickle of emails.

For a client with multiple accounts, payroll, multi-state sales tax, or a cleanup situation, plan on three to six weeks before the books are genuinely current and reconciled. Set that expectation up front: clients told "this takes a few weeks to do right" are patient; the ones who expected instant magic are not.

FAQ

What documents do you need to onboard a new bookkeeping client?

At minimum: entity formation docs and the EIN letter, the most recent business tax return, access to the existing accounting file and chart of accounts, statements and access for every bank and credit card account, loan agreements with amortization schedules, payroll access, sales tax registrations, merchant account details, and accountant access to their software.

How long does it take to onboard a new bookkeeping client?

A clean, simple client can be onboarded in one to two weeks, limited mostly by how quickly they send documents. A client with payroll, multiple accounts, multi-state sales tax, or a cleanup backlog usually takes three to six weeks to get current and reconciled.

How do I make sure I don't miss a bank or credit card account during intake?

Don't rely on the client's memory. Cross-check the prior-year return for interest income and expense, and scan the main checking account for transfers and card payments. The forgotten account usually shows up in the transfer trail.

What should I collect before sending the engagement letter?

Enough to scope and price accurately: entity type, approximate transaction volume, number of accounts, whether there's payroll and sales tax, and the current state of the books. That prevents underpricing a job that turns out to be a cleanup.

Get every document without the email chase

BookkeeperCollect lets you build this onboarding checklist once, send each client a branded upload portal link, and get automatic reminders that chase missing items until everything's in. Instead of a dozen back-and-forth emails, the client sees exactly what to send and uploads it in one place. Try it free for 14 days on your next onboarding.