How to Build a Legal Billing App with Bubble

Law firms lose revenue every month to un-billed time entries, invoice disputes, and manual billing processes. A purpose-built legal billing app closes those gaps, and Bubble provides everything needed to build one without a custom development team.

This guide covers the full build: data model, time tracking workflows, invoice generation, trust accounting, plugin stack, and realistic costs.

Key Takeaways

• Time tracking is the foundation: Every billable event must be captured at the time entry level before invoicing, reporting, or trust account management can function correctly.
• Matter-based billing requires a clean data hierarchy: Clients contain matters; matters contain time entries and expenses; invoices aggregate them. This hierarchy must be modelled correctly in Bubble.
• Billing rates need flexibility: Different attorneys bill at different hourly rates; some clients have negotiated flat fees or blended rates. The rate structure must be modelled in the data, not hardcoded in workflows.
• Stripe handles payment collection and trust accounting: Use Stripe for invoice payments and separate Stripe accounts for IOLTA trust fund management to maintain proper client fund separation.
• Automation reduces revenue leakage: Scheduled workflows that flag un-billed time entries and overdue invoices prevent the revenue losses that manual billing processes create.

What Is a Legal Billing App — and Why Build It with Bubble?

A legal billing app tracks billable time, manages client matters, generates invoices, and collects payments for legal services. It differs from general invoicing software in important ways, including matter-based time tracking, flexible billing rate structures, trust accounting, and court cost recovery.

General invoicing tools like QuickBooks or FreshBooks handle basic billing but aren't built for attorney hourly rates, IOLTA compliance, or retainer drawdown workflows.

Before committing to building in Bubble, reviewing Bubble's pros and cons is worth the time, particularly for financial applications where reliability and data integrity are non-negotiable.

• Solo attorneys use it to log time against matters, generate invoices, and collect payments without the overhead of expensive legal practice management software.
• Small-to-mid law firms use it to centralise time tracking across multiple attorneys, manage matter billing rates, and generate firm-wide billing reports.
• Legal aid organisations use it for client billing on sliding-scale fee structures, expense recovery, and donor-funded matter reporting.
• Boutique practices build a custom billing app in Bubble to match their exact billing workflow rather than adapting to the constraints of off-the-shelf practice management software.

Bubble's relational data model, Stripe integration, and PDF Conjurer plugin cover the core legal billing stack without custom development.

What Features Should a Legal Billing App Include?

Legal billing requires more than an invoice generator. The feature set spans time capture, rate management, invoice creation, payment collection, and trust accounting, with each stage building on the last.

A working MVP needs matter management, time entry logging, invoice generation, and Stripe payment collection. Trust accounting and QuickBooks sync are phase two features.

• Client and matter management: Client records contain contact details, billing preferences, and a list of linked matters. Each matter tracks the responsible attorney, billing method, status, and a running balance of unbilled time.
• Time entry logging: Attorneys log time entries against specific matters with date, duration (in decimal hours), description, and a billable flag. Rate selection pulls from the applicable BillingRate record automatically.
• Expense tracking: Court filing fees, travel costs, and third-party expenses log as separate Expense records linked to the matter with a receipt upload, amount, category, and billable flag.
• Billing rate management: A BillingRate data type stores rate configurations per attorney, per matter, or per client, supporting hourly, flat fee, and blended rate structures. Rates have effective dates to handle rate changes over time.
• Invoice generation: The billing manager selects a client and matter, and a workflow aggregates all unbilled, billable time entries and expenses into an Invoice record. PDF Conjurer renders a formatted invoice PDF.
• Invoice delivery and payment collection: Generated invoices send via SendGrid to the client's billing email with a Stripe Checkout link. The client pays online; a webhook updates the invoice status and creates a Payment record.
• Trust account and retainer management: Retainer deposits collect into a TrustAccount record per client. Invoice payments drawn from retainer deduct the balance and create a trust Payment record distinct from operating account payments.
• Billing reports: A reporting dashboard shows work-in-progress (unbilled time by attorney and matter), accounts receivable aging, collections by time period, and attorney productivity metrics.

How Do You Structure the Database for a Legal Billing App in Bubble?

The billing data hierarchy is the core architectural decision. Get the Client-Matter-TimeEntry-Invoice relationship right and every workflow follows naturally.

Model the hierarchy top-down: Client contains Matters; Matters contain TimeEntries and Expenses; Invoices aggregate selected TimeEntries and Expenses from one or more Matters.

• Client: Fields for name, contact email, billing email, phone, billing rate type (Option Set: Standard, Negotiated, Flat Fee), retainer balance (number), billing notes, and a list of linked Matters. The top-level billing entity.
• Matter: Fields for linked Client, matter name, matter type (Option Set: Litigation, Contract, Estate, Corporate, Employment), responsible attorney (User), billing method (Option Set: Hourly, Flat Fee, Contingency), status (Option Set: Active, Closed, On Hold), and running unbilled amount (number calculated from linked TimeEntries).
• TimeEntry: Fields for linked Matter, billing attorney (User), entry date, hours (number in decimal format), description, billing rate (number from BillingRate lookup), billable (yes/no), billed (yes/no, updated when invoice is generated), and linked Invoice (empty until billed).
• Expense: Fields for linked Matter, date, description, amount, category (Option Set: Filing Fee, Travel, Court Reporter, Expert Witness), billable (yes/no), billed (yes/no), receipt file, and linked Invoice.
• BillingRate: Fields for attorney (User), client (Client), matter (Matter), rate type (Option Set), hourly rate (number), flat fee amount (number), and effective date. Rate lookup priority: matter-specific rate first, then client rate, then attorney default rate.
• Invoice: Fields for linked Client, linked Matters (list), linked TimeEntries (list), linked Expenses (list), subtotal, tax amount, total, status (Option Set: Draft, Sent, Paid, Overdue, Void), issue date, due date, paid date, and invoice PDF file.
• Payment: Fields for linked Invoice, amount, payment date, payment method (Option Set: Card, Check, Wire, Trust Drawdown), Stripe payment intent ID, and type (Option Set: Operating, Trust). Critical for IOLTA separation.
• TrustAccount: Fields for linked Client, current balance (number), linked Payment list, IOLTA flag (yes/no), and last reconciled date. Tracks client retainer funds separate from firm operating revenue.

How Do You Build the Core Workflows for a Legal Billing App in Bubble?

These seven workflows power the complete legal billing cycle, from time capture through invoice generation, payment collection, and trust account management.

The most common build mistake is calculating rates at invoice time rather than capturing them at time entry. Lock the rate on the TimeEntry record when it's created.

• Time entry logging: When attorney submits the time entry form, a workflow looks up the applicable BillingRate (checking matter-specific rate first, then client rate, then attorney default), creates a TimeEntry record with the rate locked at the current value, and updates the matter's running unbilled total.
• Expense capture: When attorney submits an expense, a workflow creates an Expense record with the receipt file, links it to the matter, and updates the running unbilled expense total on the matter record.
• Invoice generation: When billing manager clicks Generate Invoice, a workflow aggregates all TimeEntry records where linked Matter = selected matter and billed=no and billable=yes, plus all Expense records with the same filters. It creates an Invoice record, calculates subtotals, generates a PDF via PDF Conjurer, and marks all aggregated entries as billed.
• Invoice delivery: When billing manager clicks Send Invoice, a backend workflow sends the invoice PDF via SendGrid to the client's billing email with a Stripe Checkout payment link embedded. Invoice status updates to Sent.
• Online payment collection: When client pays via the Stripe Checkout link, Stripe fires a webhook to a Bubble API endpoint. A backend workflow creates a Payment record (type: Operating), updates Invoice status to Paid, records the paid date, and sends a payment confirmation email via SendGrid.
• Retainer drawdown: When an invoice is to be paid from the client's retainer, a workflow checks that TrustAccount balance is sufficient, deducts the invoice amount from the TrustAccount balance, creates a Payment record (type: Trust Drawdown), and updates the Invoice status to Paid.
• Unbilled time and overdue invoice alerts: A scheduled backend workflow runs weekly. It checks for TimeEntries older than 30 days with billed=no and billable=yes, and sends a SendGrid alert to the billing manager listing outstanding unbilled time. A separate scheduled workflow checks for Invoices with status=Sent and due date past today, updates status to Overdue, and sends an overdue notice to the client.

What Security and Data Requirements Apply to a Legal Billing App?

Legal billing apps handle financial data, client payment information, and trust account balances. Security configuration must reflect both data privacy requirements and financial compliance obligations.

IOLTA trust accounting has specific regulatory requirements in most US jurisdictions. The software architecture must support strict fund separation.

For a detailed walkthrough of privacy rules and data access controls in Bubble, the guide on securing data in Bubble covers the implementation approach.

• Client billing isolation: If clients have portal access, privacy rules restrict their view to Invoice, Payment, and Matter records where the linked Client field matches their own User account. No client sees another client's billing data.
• Attorney time entry scoping: Attorneys see only TimeEntry records where they are the billing attorney. Partners and billing managers access all TimeEntries via a separate role condition in the privacy rule.
• Financial data security: Bubble never stores card numbers, bank account details, or other PCI-scoped financial data. Stripe manages all payment processing. Bubble only stores Stripe payment intent IDs and status fields.
• IOLTA trust account separation: Trust funds and operating funds must remain strictly separated. Model this in Bubble by using the Payment type field (Trust vs. Operating) and by connecting to separate Stripe accounts for each fund type. Never mix trust and operating payment records in reporting.
• Invoice immutability: Once an Invoice reaches status=Paid, edit and delete permissions should be removed from all roles via privacy rules. Paid invoices should be permanent records.
• Audit trail: A PaymentLog data type records every payment event, trust account transaction, and invoice status change with a timestamp and the User who triggered it. This type has no edit or delete permissions.

What Plugins and Integrations Does a Legal Billing App Need?

A legal billing app's plugin stack centres on Stripe for payments and PDF Conjurer for invoice generation. The other integrations extend functionality for notification delivery and accounting software sync.

Establish Stripe and PDF Conjurer first. These are the two most complex integrations; validate them before adding secondary plugins.

• Stripe plugin (official Bubble plugin): Handles all invoice payment collection via Stripe Checkout. Configure Stripe webhook delivery to a Bubble API endpoint for payment confirmation events. For retainer billing, Stripe Billing manages recurring monthly deposits.
• PDF Conjurer: Generates formatted invoice PDFs with firm branding, matter details, itemised time entries and expenses, billing rate breakdown, and payment instructions. Build one PDF Conjurer template per invoice type.
• SendGrid plugin (official): Delivers invoice emails, payment confirmations, overdue notices, and unbilled time alerts. Create named email templates in SendGrid for each notification type to maintain consistent formatting.
• Bubble File Uploader element: Stores expense receipts and any supporting documents attached to billing records. Set allowed file types to PDF, PNG, and JPG with a reasonable size cap.
• QuickBooks API (via API Connector): Syncs Invoice and Payment records from Bubble into QuickBooks Online for firm accounting. Set up the API Connector with QBO's OAuth authentication and configure sync triggers on invoice creation and payment recording.
• Air-Date Picker plugin: Improves date input UX for time entry date selection, invoice issue and due dates, and expense date fields beyond Bubble's default date input element.
• Bubble backend scheduler: Runs the unbilled time alert and overdue invoice reminder workflows on a weekly schedule. No additional plugin required, configure in the Bubble backend workflow editor.
• Twilio plugin: Sends SMS payment reminders to clients with overdue invoices. Particularly effective for clients who respond to text faster than email.

How Long Does It Take and What Does It Cost to Build a Legal Billing App with Bubble?

Build time depends primarily on the complexity of billing rate structures, the depth of trust accounting required, and whether a client-facing portal is included.

An MVP with time tracking, matter management, invoice generation, and Stripe payment collection is achievable in 8–12 weeks for a self-builder. Trust accounting and QuickBooks sync add significant complexity.

Bubble plan requirements are driven by the automation layer. Scheduled workflows for unbilled time alerts and overdue invoice reminders require the Growth plan as a minimum.

• Growth plan ($29/month): Minimum for backend scheduled workflows. Essential for automated billing alerts and overdue reminders.
• Stripe fees: 2.9% + $0.30 per invoice payment. If monthly billing volume is significant, this becomes a meaningful cost to factor into product pricing.
• PDF Conjurer: Free tier available; production invoice volume typically requires a paid plan.
• QuickBooks Online API: Requires a QBO plan that includes API access. Most paid QBO plans include API access; confirm before architecture decisions.
• SendGrid: Free tier at 100 emails/day. A firm billing 20+ clients monthly will likely need the paid Essentials plan.

For a practical guide to scoping and launching a first version without over-engineering, Bubble MVP development covers the decisions that matter most at the early stage.

Conclusion

Bubble enables any law firm to close the gap between logged time and collected revenue with a custom billing system built around the Client-Matter-TimeEntry hierarchy.

Start with time tracking, matter management, and invoice generation with Stripe. Add trust accounting and QuickBooks sync once the core billing cycle is validated against real billing scenarios.

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Want Your Legal Billing App Built to Handle Real Firm Revenue?

Trust accounting separation that breaks under retainer drawdown, billing rate lookup that defaults to the wrong rate, and a QuickBooks sync that duplicates records are the failure modes that have direct revenue and compliance consequences.

At LowCode Agency, we build Bubble apps as a full product team - not a dev shop that hands off code. We scope the architecture, engineer the workflows, and stay involved through launch and beyond.

• Data architecture: We design your data types, option sets, and privacy rules before writing a single element on the canvas.
• Workflow engineering: We build backend workflows, scheduled jobs, and API integrations with proper logic and error handling.
• Plugin configuration: We select and configure the right Bubble plugins for your feature set without unnecessary bloat.
• Role-based access: We implement privacy rules at the database level, not just conditional UI visibility.
• Integration setup: We connect your Bubble app to Stripe, SendGrid, Twilio, and other services correctly from day one.
• Pre-launch testing: We test against real data before deployment so every workflow performs correctly under live conditions.
• Post-launch support: We stay involved after go-live to optimize as real usage data shapes the app.

We have built 350+ products for clients including Coca-Cola, American Express, Sotheby's, and Medtronic. We know exactly where Bubble builds fail and we address those problems before they surface.

If you want your Bubble app built correctly from day one, let's scope it together.