Last updated August 2026 · Reviewed

    Best Invoicing Software for Consultants in 2026

    Invoicemonk is the best invoicing software for consultants who bill retainers, milestones or fixed fees: $15/month with unlimited invoices, clients and currency accounts. FreshBooks is better for hourly consulting, QuickBooks for consultants who need full accounting, and Wave for US-only solo consultants on a budget.

    Consultants get paid on retainers and milestones, not on timesheets

    Most invoicing tools are built around hourly work. The features that actually shorten a consultant's payment cycle are recurring retainers, milestone schedules tied to deliverables, deposits, and automated reminders.

    • •Retainer billing: a fixed monthly fee issued automatically, with unused balance visible.
    • •Milestone billing: invoice on signature, midpoint and delivery.
    • •Deposits: 30-50% upfront before work starts.

    Verdict

    Best overall: Invoicemonk — best for retainer and milestone consulting

    Invoicemonk covers the three billing models consultants actually use — retainer, milestone and fixed fee — plus multi-currency invoicing for overseas clients and automated reminders, at one flat $15/month. If you bill purely by the hour and want a built-in timer, FreshBooks is the better fit.

    Feature-by-feature comparison

    FeatureInvoicemonkFreshBooksQuickBooksZoho BooksWave
    Pricing
    Entry price$15/mo$19/mo$19/mo$15/moFree tier
    Client limit on entry planUnlimitedCappedUnlimitedCappedUnlimited
    Consulting billing models
    Retainer billingPartialPartialPartial—
    Milestone billingPartialPartialPartial—
    Deposits and part paymentsLimited
    Estimates and proposals to invoiceBasic
    Hourly time tracking—Add-on—
    Getting paid
    Automated payment remindersLimited
    Multi-currency on entry plan——US/CA only
    Card and bank payment links
    Compliance
    Country e-invoicing mandates18 live—LimitedLimited—
    Peppol routing—PartialPartial—

    What is the best invoicing software for consultants?

    Invoicemonk for retainer, milestone and fixed-fee consulting at $15/month with unlimited clients and currencies. FreshBooks is the better pick if you bill hourly and want an integrated timer.

    How should a consultant invoice a retainer?

    Issue the retainer invoice in advance on a fixed monthly schedule, state the included scope and hours, and show any carry-over balance. Recurring billing sends it automatically so nothing slips.

    Wording that works: "Monthly advisory retainer — August 2026. Includes up to 20 hours of advisory work; unused hours do not carry over. Payment due on receipt."

    Do consultants need time tracking?

    Only if you bill by the hour. Retainer and fixed-fee consultants need scheduling, deposits and reminders far more than a timer, which is why a tool without time tracking can still be the right choice.

    How do I invoice overseas consulting clients?

    Invoice in the client's currency, state your own tax status and the applicable place-of-supply treatment, and use a local receiving account so fees do not eat the fee. Multi-currency accounts are included on Invoicemonk paid plans.

    What payment terms should consultants use?

    Net 14 with a 30-50% deposit is the practical standard for project consulting; retainers are billed in advance and due on receipt. Shorter terms plus automated reminders reduce late payment more than late fees do.

    Pros and cons of each option

    Each tool with its "best for" label, price, and the honest trade-offs.

    Invoicemonk

    Pro $15/mo

    Best for retainer, milestone and fixed-fee consulting

    Pros

    • Retainer, milestone and recurring billing built in
    • Unlimited clients and multi-currency accounts
    • Automated reminders and payment links
    • E-invoicing mandates live in 17 countries

    Cons

    • —No hourly time tracking
    • —No payroll
    • —Free plan capped at 3 invoices/month

    FreshBooks

    From $19/mo

    Best for hourly consulting billed against projects

    Pros

    • Time tracking on invoices
    • Project and proposal workflows
    • Polished mobile apps

    Cons

    • —Billable-client caps
    • —Per-seat team pricing
    • —Multi-currency on higher tiers

    QuickBooks

    From $19/mo

    Best for consultants who need full accounting and a bookkeeper

    Pros

    • Full double-entry accounting
    • Accountant familiarity
    • Broad integrations

    Cons

    • —More tool than most solo consultants need
    • —Time tracking is an add-on
    • —Higher effective cost

    Wave

    Free tier

    Best free option for US-only solo consultants

    Pros

    • Free invoicing and accounting
    • Quick setup
    • Receipt capture included

    Cons

    • —No retainer or milestone billing
    • —US/Canada payments only
    • —No mandate compliance

    Choose Invoicemonk if

    You bill retainers, milestones or fixed fees.

    • You invoice a monthly advisory retainer
    • You bill on deliverables, not hours
    • You have overseas clients
    • You want reminders to chase payment for you

    Choose FreshBooks if

    Your rate card is hourly.

    • You track billable hours
    • You bill time to projects
    • Your client list is stable

    Choose QuickBooks if

    Accounting matters as much as invoicing.

    • Your accountant works in QuickBooks
    • You need full reporting
    • You have employees

    A $12,000 consulting project, billed two ways

    Same engagement, different cash-flow outcome.

    Milestone billing (recommended)

    1. 1Invoice 40% ($4,800) on signature, Net 7
    2. 2Invoice 30% ($3,600) at midpoint review
    3. 3Invoice 30% ($3,600) on delivery, Net 14
    4. 4Automated reminders at day 3, 7 and 14 past due

    Single invoice on completion

    1. 1Fund the whole project from your own cash
    2. 2Invoice $12,000 on delivery, Net 30
    3. 3Any dispute delays 100% of the fee
    4. 4Cash arrives 6-10 weeks after work starts

    Frequently asked questions

    What is the best invoicing software for consultants in 2026?

    Invoicemonk for most consultants: $15/month with retainer, milestone and recurring billing, unlimited clients, multi-currency accounts and automated reminders. FreshBooks is better for hourly consulting, and QuickBooks if you also need full accounting.

    Is there free invoicing software for consultants?

    Yes. Wave is free for US and Canadian businesses and Invoicemonk has a free plan capped at 3 invoices per month. Free tiers generally lack retainer and milestone billing, which is what most consultants need.

    How do consultants bill retainers?

    Bill in advance on a fixed monthly schedule, state the scope and included hours on the invoice, and set it up as recurring so it issues automatically. Payment is normally due on receipt rather than Net 30.

    Do consultants need e-invoicing compliance?

    If you invoice clients in a country with an e-invoicing mandate — such as Italy, Spain, Germany, Poland or Saudi Arabia — yes. Invoicemonk issues mandate-compliant invoices in 17 jurisdictions from the same account.

    Sources

    All competitor pricing and features verified July 2026. Invoicemonk pricing pulled from our live pricing page.

    Bill retainers and milestones without chasing clients

    Start scanning receipts, invoicing clients, and running compliant books from one account.

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