How to Migrate from a Manual or Homegrown Billing System

Why This Migration Can’t Wait

• You’re billing clients with a script someone wrote two years ago.
• Each renewal needs a spreadsheet, a Slack thread, and three approvals.
• Finance can’t close books without hunting down product usage.
• Every invoice sent is a minor miracle—and one misstep from audit exposure.

This isn’t a system. It’s a bottleneck waiting to break. Time to migrate—before scale makes the decision for you.

• You are spending 20-30 hours at month-end generating invoices
• Upgrades from free trials and freemium to paid plans are being missed
• Ramp/step-up deals with scheduled price increases aren’t being adjusted
• Incoming cash flows are being delayed because invoices are sent 2 weeks late

1. Map Your Current Billing Workflows in Detail

Before you make a change, you need to understand exactly how your current billing process is working.

• Document every step: sales closed-won, contract signature, billing models, invoicing, payment collection, revenue recognition
• Identify where data originates: CRM, product subscription databases, usage logs, finance spreadsheets, APIs
• Tag current workflows as: manual, semi-automated, or fully automated
• Identify failure points: late invoices, usage mismatches, manual adjustments, lost revenue

Without a complete understanding map of your current billing process, you may end up introducing billing errors and upsetting customers when you upgrade to a commercial application.

2. Build a Future State Billing Roadmap with Business and Technical Owners

Billing is one of the most important functions in your business.  It is how you bring in the cash to run your day-to-day operations.  SaaS billing touches Sales, Finance, Engineering, Product, and Customer Success. Migration to a commercial billing platform requires a cross-functional team.

• Appoint a Billing Project Lead—ideally from Finance Ops or RevOps
• Assign system owners for data sources: CRM, ERP, product usage, payment gateways
• Outline the phased rollout: sandbox config → test billing cycles → parallel run → full cutover
• Create a rollback plan in case of system failure or critical issues

Successful migrations are treated like ERP projects: scoped, staged, and fully owned.

3. Standardize Your Product Catalog and Pricing Logic

One of the biggest challenges with spreadsheets and homegrown billing systems is the lack of standardization of products, plans, prices, and discounts.  Migration to a new commercial billing system is your opportunity to clean the data up.

• Consolidate SKUs and standardize naming conventions
• Define billing rules for each product (e.g., fixed, usage-based, milestone, hybrid)
• Remove or flag legacy SKUs that are no longer sold
• Map each SKU to the right rev rec treatment and GL account

Don’t bring chaos into the new system. Normalize first. Automate second.

4. Configure Your Billing System Based on Actual Business Rules

Avoid re-producing spreadsheet hacks in software. Instead:

• Define contract lifecycle: start, pause, amend, renew, terminate
• Build billing event triggers: usage thresholds, milestone completions, calendar schedules
• Implement approval workflows for credits, refunds, and discounts
• Set up integrations with CRM, ERP, payment processor, and usage data source

System configuration should mirror operational reality—not idealized process charts.

5. Run Parallel Billing Before Going Live

Remember that 1) billing is a customer-facing system and 2) it drives cash flow in the business. Don’t rush the switch over.  Test, test, test before cut over.

• Select a 1–2 month period of historical data and re-run it through the new billing system
• Compare outputs: invoice line items, sub-totals, taxes, passthrough charges, and grand totals
• Reconcile differences and identify the root causes of differences in calculations- Validate edge cases: contract amendments, mid-month upgrades with prorations, usage fees

Only go live when confidence is high, discrepancies are explained, and workflows are stable.

6. Train Stakeholders and Set Post-Go-Live Monitoring

No migration is complete without change management.

• Train accounts receivable, customer support, and sales teams on what changed and what’s expected
• Create documentation: how to handle credits/refunds, where to view invoices, when to escalate
• Monitor billing logs, sync errors, and invoice exceptions daily for 30–60 days
• Schedule weekly post-launch check-ins to review issues and stabilize adoption

Billing system success isn’t about launch. It’s about sustained accuracy at scale.