You approve an invoice in your CRM for ₹50,000. Two days later your accountant flags it in Xero or QuickBooks as ₹51,200. You ask your team what happened. Nobody knows. This happens to nearly every business running separate CRM and accounting systems, and it kills cash flow visibility, breaks tax compliance, and makes month-end close a guessing game. The problem is not usually that one system is wrong—it's that they're calculating different things, and nobody documented where the gap happens. Tax gets applied at a different stage. Currency conversions happen on different dates. Proration logic lives in one place but not the other. By the time you notice, the discrepancy is buried under a week of transactions. Here are the five places invoice amounts actually split between systems, how to spot each one, and a monthly audit process that catches them before your accountant does. Tax calculations applied at different stages This is the most common source of drift. Your CRM calculates tax on the pre-discount subtotal. Your accounting software applies tax only after a discount coupon. Or one system treats tax-inclusive pricing, the other applies it on top. Example: A ₹10,000 invoice with a 10% discount. CRM path: ₹10,000 − 10% discount = ₹9,000. Then 18% GST = ₹10,620 total. Accounting path: ₹10,000 at 18% GST = ₹11,800. Then 10% discount applied to the full amount = ₹10,620 total. Both land on ₹10,620, but only because the math worked out symmetrically. Change the discount to 12% and you get ₹10,517 in one system and ₹10,384 in the other. Southeast Asia makes this harder. Malaysia (SST), Singapore (GST), and Indonesia (PPN) each have different rules on whether tax applies before or after discounts, and whether tax-exempt items are itemized or bundled. Your CRM's tax engine may not know these rules. Your accounting software almost certainly does—but only if you configured it correctly. How to spot this: Pull five random invoices from last month. Recalculate the tax manually on paper. If your CRM total doesn't match the manual calculation, the tax rule is wrong in your CRM. Do the same for your accounting software. Multi-currency conversions on different days If you invoice in USD but your accounting system records in SGD or INR, the conversion rate matters. A ₹50,000 invoice created in your CRM on Monday might convert at a rate of 0.0121 USD per rupee. By Wednesday, when your accounting software syncs the transaction, the rate is 0.0119. The invoice amount in your home currency is now ₹51,300—and you never touched it. This is especially painful when invoices span multiple currencies. You invoice a client in AUD, they pay in USD, your accounting records in SGD, and your CRM is set to display in INR for reporting. Each handoff introduces a new rate and a new rounding rule. Most CRM-to-accounting integrations pick one rate—usually the rate on the day the invoice is created—and lock it. But if your accounting software uses the rate on the day of payment or the day of reconciliation, the numbers will drift. How to spot this: Look at a multi-currency invoice created two weeks ago. Write down the invoice amount in the CRM. Write down the converted amount in your accounting software. Calculate what rate would make the CRM amount equal the accounting amount. If the rate is materially different from your company's spot rate on either the invoice date or the reconciliation date, something is wrong. Prorations and mid-cycle changes Subscription billing loves prorations. A client signs up on the 15th of a monthly billing cycle. You want to charge them half price for the first month, then full price from month two. Your billing system calculates ₹25,000 for the prorated period. But if that prorated invoice is synced to your accounting software as a full ₹50,000 transaction, then reversed, then replaced with the correct amount, you'll have three line items instead of one—and mismatched totals depending on which system you're reading from. This gets worse with seat-based pricing changes. A client had 5 users at ₹5,000 each (₹25,000 total). On the 20th they add 3 more users. Do you: Issue a new invoice for the incremental users for the remainder of the month? Hold the change until the renewal and issue a single renewal invoice at the new seat count? Merge the pro-rata charge into the original invoice? Whichever you choose in your CRM, your accounting software may not handle it the same way. One system shows a single ₹34,500 invoice (the pro-rata add-on), the other shows two invoices (the original ₹25,000 plus a ₹9,500 amendment). How to spot this: Search your CRM for invoices created or modified on days 14–20 of your billing cycle. For each one, check whether the amount in your CRM matches the amount in your accounting software. If there are multiple line items or reversals in either system, manually add them up to confirm the net total. Metadata that doesn't sync Your CRM might track an invoice's due date, payment terms, or cust