Series A changes four things at once: headcount, cash balance, accountability, and the number of people who can spend company money.
Build the core systems before or alongside your first finance hire, or they'll spend two quarters cleaning up instead of building.
Sequence by dependency, not urgency: banking and payroll first, then the general ledger, then AP, cards, and treasury.
Evaluate tools on integration rather than features. Your real cost is the manual work between systems that don't connect.
Payroll is a finance decision, not just an HR one. It's usually your largest recurring outflow and carries tax compliance obligations.
Set a month-end close target and hold to it. Ten business days is a reasonable start.
Collect W-9s before the first vendor payment, not during January's 1099 scramble.
Seed-stage finance runs on improvisation. One bank account, a founder's card, a spreadsheet, and a bookkeeper who reconciles it monthly. That works until it doesn't.
Series A is the inflection point. Headcount jumps, the cash balance becomes large enough that where it sits matters, your board expects reporting on a schedule, and the number of people who can spend company money goes from two to twenty. The systems that got you here quietly stop working, usually about a quarter after they should have been replaced.
This is what to have in place within 90 days of closing, and what tends to go wrong.
Why Series A is the inflection point
Four things change at once.
Headcount. You're hiring across functions, often in multiple states. Payroll stops being a rounding error and becomes your largest recurring outflow.
Cash. A balance that used to be measured in months of runway is now large enough that yield and insurance coverage are real decisions rather than theoretical ones.
Accountability. You have a board, investor reporting obligations, and eventually an audit. Reconstructing numbers after the fact gets expensive fast.
Spend surface. More people, more vendors, more subscriptions, more cards. Without policy and controls, spend visibility degrades faster than headcount grows.
The failure mode isn't dramatic. It's a slow accumulation of manual work until your first finance hire spends their first two quarters cleaning up instead of building.
The 90-day checklist
Business banking and cash management
Move from one account to a deliberate structure: operating cash for near-term expenses, and reserves for everything you won't touch this quarter. Get clear on FDIC coverage limits and how your provider handles balances above them.
Set up proper access controls while you're at it. Founder-only banking access is a single point of failure, and shared credentials are an audit finding waiting to happen.
Also decide who has payment authority, at what thresholds, and who approves exceptions.
Corporate cards and an expense policy
Issue cards with limits and category controls rather than handing out a shared card number. The policy matters more than the plastic: write down what's reimbursable, what needs pre-approval, what receipt threshold applies, and what happens when someone ignores it.
Two things worth automating early are receipt capture and transaction coding. Both are cheap to set up now and miserable to backfill.
Payroll setup
Decide who owns payroll operationally, what cadence you'll run, and which platform handles it. If you're hiring across state lines, confirm the registration process for each new state, because payroll obligations generally follow where the employee works rather than where you're incorporated.
Clarify which tax filings your provider submits and which stay your responsibility. That line is where liability sits, and it varies by provider.
Accounts payable and bill pay
Get vendor invoices into one queue with an approval path. At Series A, the specific goals are eliminating founder-approves-everything as a bottleneck, capturing W-9s before the first payment rather than during January's 1099 scramble, and keeping payment timing deliberate instead of reactive.
Treasury and cash yield
Once you're holding meaningful cash, idle balances have an opportunity cost. Decide your policy: how much stays fully liquid, what your risk tolerance is, and who signs off on moving money.
Write it down and share it with your board. Treasury decisions made without a stated policy are the ones that get questioned later.
Financial reporting and month-end close
Set a target close date and hold to it. Ten business days is a reasonable early goal; five is achievable once systems are connected.
Define the recurring package now: cash position, burn and runway, revenue, and budget-versus-actual. Consistency matters more than sophistication, because the value comes from comparing months.
Accounting software
If you're still on cash-basis bookkeeping in a spreadsheet, this is the quarter to move. Pick a general ledger and connect it to your banking, card, AP, and payroll systems so transactions flow in with coding intact.
The integration is the point. A general ledger fed by manual CSV imports produces the same numbers with far more work and more room for error.
Audit readiness basics
You may not need an audit yet. You will. The habits that make one cheap are boring and start now: keep contracts and vendor agreements somewhere findable, retain payroll and tax records to the longer of the applicable requirements, document who approved what, and don't commingle personal and business spend.
Keep a cap table that matches your legal documents. Reconciling those two later is a common and avoidable expense.
Common mistakes in the first 90 days
Hiring a finance lead before building the systems. A strong first finance hire will build the stack. A stack that doesn't exist means they spend two quarters on cleanup.
Treating payroll as purely an HR decision. Payroll is your largest cash outflow and a tax compliance obligation. It belongs in the finance conversation.
Leaving all cash in one operating account. It's the default, and it's a decision you made by not making it.
Writing an expense policy nobody reads. A policy enforced by system controls works. A policy in a document does not.
Delaying month-end close. Every month you don't close is a month you'll reconstruct under time pressure, usually during diligence.
Adding tools that don't talk to each other. Six best-in-class products with no integrations produce more manual work than four that connect.
Skipping W-9 collection. Paying a contractor without a W-9 on file guarantees a January problem.
How to choose tools: integration first, not features first
The instinct is to evaluate each category separately and pick the best product in each. At Series A that's usually the wrong optimization.
Your real cost isn't the software. It's the hours someone spends moving data between systems that don't connect, and the errors introduced when they do it by hand. A tool with 80% of the features and a real integration into your general ledger typically beats one with 100% of the features and a CSV export.
Practical questions to ask about anything you're evaluating:
Does it write to our general ledger automatically, with coding intact?
Does it work at 50 people, not just at 10?
What does it cost at our real headcount, including per-user or per-employee fees?
Can we get our data out if we leave?
Who owns it internally, and what happens when that person is on vacation?
Then sequence by dependency rather than urgency. Banking and payroll come first because everything else references them. Accounting software comes next because it's the destination for everything. AP, cards, and treasury layer on top.
Get the order right and each addition takes days. Get it wrong and you'll rebuild integrations twice.
Frequently asked questions
What financial systems does a Series A startup need?
Business banking with a deliberate account structure, corporate cards with an expense policy, payroll, accounts payable and bill pay, a treasury or cash policy, a general ledger with connected integrations, a defined month-end close, and basic audit-readiness habits like record retention and approval documentation.
How long should month-end close take at Series A?
Ten business days is a reasonable early target, and five is achievable once your banking, card, AP, and payroll systems feed your general ledger automatically. What matters most is picking a target and holding to it, since the value of the close comes from comparing consistent months.
Should we hire a finance lead or build the systems first?
Build the core systems first, or at least in parallel. A strong first finance hire will build and improve the stack, but if nothing exists they typically spend their first two quarters on cleanup instead of forecasting, reporting, and planning.
When should a startup set up a treasury or cash policy?
Once your balance is large enough that idle cash has a meaningful opportunity cost and exceeds standard deposit insurance limits. Write down how much stays fully liquid, what risk you'll accept, and who approves moving money, then share it with your board before you act on it.
What's the most common financial operations mistake after a Series A?
Adding tools that don't integrate. Six best-in-class products with no connections create more manual work than four that talk to each other, and the hidden cost is the hours spent moving data plus the errors that come from doing it by hand.
Do we need to be audit-ready at Series A?
Most Series A companies don't need an audit yet, but the habits that make a later audit cheap start now: findable contracts, retained payroll and tax records, documented approvals, no commingling of personal and business spend, and a cap table that matches your legal documents.