On paper, balances between related companies should always net to zero. If Company A shows a $40,000 receivable from Company B, Company B's books should show a matching $40,000 payable back. In real life, those two numbers drift apart almost every month — and almost never because anyone did anything wrong. It's timing.

1. The two companies record it on different days

If Company A books a transfer on the last day of the month, but Company B doesn't record it until the money actually clears in the new month, the two sets of books will disagree at every month-end close until someone catches it.

2. Rounding on shared costs

Shared expenses split by percentage — rent, payroll processing, software subscriptions — can create small rounding differences every time they're divided between companies. A few cents a month turns into real money over a year if nobody reconciles it.

3. A transfer recorded on one side, not the other

Every transfer between companies needs a matching entry on both sides. When one gets entered but never mirrored on the other — often because different people or different systems manage each company — the gap doesn't close on its own. It grows.

4. The two companies track it differently

If Company A logs intercompany activity one way and Company B logs it another, matching the two becomes a manual, error-prone job every single time — which is exactly when things slip through.

5. Manual entries with nothing to check them against

When intercompany entries are keyed in from memory or a quick note, instead of one shared record of what actually moved and when, the two companies' books end up telling two different stories about the same transaction.

A monthly routine that keeps balances at zero

  • Keep one shared log of every transfer between companies — date, amount, and both companies involved — that both sets of books get entered from.
  • Reconcile the receivable/payable pair between every related company at each month-end close, not just at year-end.
  • Flag any balance that doesn't net to exactly zero the same month it shows up, before it rolls forward.
  • Use the same chart-of-accounts treatment for intercompany activity across every company in the group.
  • Review your allocation percentages once a year to make sure they still add up to 100%.

Most drift between related companies isn't a red flag — it's what happens when separate books are kept by separate people. The fix isn't more oversight. It's one line-by-line reconciliation between the companies, on a fixed schedule.