At Series A the books stop being for you. They are a diligence artefact, and they will be read by people looking for reasons to worry.
At a glance
The change at Series A is not volume. It is audience. Up to now the books answered your questions. From here they answer a diligence process, a board, and eventually an auditor — people reading specifically for what does not add up.
Cash basis will not survive a Series A process. Beyond that, subscription revenue has to be recognised under ASC 606 — over the period you deliver, not when the invoice is paid. A company billing annually upfront and recognising on receipt is overstating current revenue and understating deferred revenue, and diligence finds it.
An investor discovering in week three of diligence that revenue needs restating does not simply adjust the number. They adjust their confidence in every other number you gave them, at the point in the process where you have least leverage.
None of it is hard if the close has been done monthly. All of it is brutal if it is being assembled in a fortnight while also running a fundraise.
A priced round triggers a fresh 409A valuation, and option grants after it price off the new figure. You also now have a board with its own reporting cadence, which is set by them rather than by what is convenient.
Accrual close monthly with a named accountant, revenue recognised to policy and documented, board packs that reconcile, and a diligence request answered from records that already exist.