For consultants and freelancers who use a Microsoft 365 or Outlook.com Calendar and Zoho Books for their Invoices

Turn your Outlook calendar
into Zoho Books invoices

Stop copy-pasting. Cal2Bill reads your calendar events and builds your invoice automatically — in seconds.

Start free trial → See how it works

15-day free trial  ·  No credit card required  ·  $14 USD/month after

How it works

Three steps. Done.

No complex setup. No learning curve. Connect, pick, invoice.

Step 01
🔗

Connect your accounts

Sign in with Microsoft and connect your Zoho Books account. Cal2Bill only reads what it needs — nothing else is stored.

Step 02
📅

Pick your calendar events

Select a client and Cal2Bill scans your Outlook calendar for matching events. Check the ones to include — rates are calculated automatically.

Step 03
🧾

Invoice built in Zoho

Hit Build Invoice and a complete draft lands in your Zoho Books — line items, rates, taxes, and all. Review, clean, and send.

Features

Everything you actually need.
Nothing you don't.

Built for the way independent consultants actually work — not for enterprise teams with a dedicated billing department.

⚡

Smart deduplication

Already invoiced some events? Cal2Bill remembers. It adds new ones, updates changed ones, and skips duplicates — every time.

💰

Flexible billing types

Onsite hourly, service call flat fee, or offsite remote — each with its own rate and block structure. Configurable per client.

🇨🇦

Two-tax support

HST, GST+PST, GST+QST, or US sales tax. Cal2Bill handles Canadian provincial tax structures out of the box.

📦

Product & service items

Add parts, hardware, or service items to any invoice with a searchable picker — pulled directly from your Zoho Books item list.

🔒

Privacy first

Cal2Bill never stores your calendar contents, invoice data, or client names. Your billing data is yours — we just move it.

📱

Works on mobile too

Installable as a PWA on iPhone and Android. Invoice from anywhere — even from a client's site after the job is done.

Why Cal2Bill

I ran my IT consulting business for almost twenty years before the invoicing chaos finally caught up with me. Every month, the same thing — scroll back through Outlook, piece together what I did for each client, copy times into Excel, rebuild it all manually in Zoho Books. Hours gone. Repeatedly.

I kept putting it off. Weeks would pass. Then one day I sat down to do my invoicing and realized I hadn't billed some clients in well over a year. Real work, real hours — just never invoiced.

I'd been searching for a solution for most of those twenty years. Something that would just read my calendar and build the invoice automatically. Nothing existed that fit the way an independent consultant actually works. So I built it myself.

That's Cal2Bill. Simple by design — because your tools should work for you, not the other way around.

Guido Derlagen — founder of Cal2Bill
Guido Derlagen Independent IT consultant
Toronto, Canada
Pricing

Simple, honest pricing.

One product. Two billing options. No feature tiers, no paywalled essentials.

Monthly
$14 USD/mo

Billed monthly. Cancel anytime.

  • Full access to all features
  • Unlimited invoices
  • All billing types
  • Product & service item picker
  • Email support
Get started →
BEST VALUE — SAVE $24
Annual
$144 USD/yr

$12/month, billed annually.

  • Full access to all features
  • Unlimited invoices
  • All billing types
  • Product & service item picker
  • Priority email support
Get started →

15-day free trial on both plans  ·  No credit card required  ·  Trial starts on your first invoice build

Reviews

What users are saying.

Cal2Bill just launched. Be one of the first — try it free and share your experience.

💬

We're looking for beta testers.
Try Cal2Bill free for 6 months in exchange for honest feedback.

Get in touch →

⭐

Reviews from early users will appear here. Start your free trial and let us know what you think.

🚀

Built by a consultant, for consultants. If it doesn't work for your workflow, we want to hear about it.

FAQ

Common questions.

Cal2Bill works with any Microsoft 365 or Outlook.com account — this includes accounts originally created as Hotmail or Live addresses. If you use the classic Outlook desktop app, it works too, as long as it is connected to a Microsoft 365 or Outlook.com account in the background. Note: a standalone on-premise Exchange account with no Microsoft 365 or Outlook.com connection will not work.
Cal2Bill works best on Chromium-based browsers — these include Google Chrome, Microsoft Edge, Brave, and Opera. On Windows, Edge is the recommended choice as it's built-in and supports installing Cal2Bill as a desktop app. Firefox works but has limited support for the install feature. Safari works on iPhone and Mac with some limitations. Internet Explorer is not supported.
Cal2Bill only processes events that contain your client's name in the subject line and are tagged with your billing categories (like "Onsite" or "Offsite"). Everything else is completely ignored. Crucially, Cal2Bill never stores your event data — it reads, calculates, and moves on.
Cal2Bill works with any paid Zoho Books plan across all Zoho datacenters worldwide — Canada, US, EU, Australia, India, Japan, and UK. During setup, Cal2Bill automatically detects which datacenter your Zoho Books account is on and connects to the right one. No extra configuration needed regardless of where you are in the world.
Yes — you need administrator access to your Zoho Books account. Cal2Bill creates custom fields in your Zoho Books contacts during setup and creates draft invoices on your behalf. Both of these require admin-level permissions. Standard user access is not sufficient.
Your trial starts the moment you build your first invoice — not when you sign up. That means you can set up your account, configure your rates, and get familiar with the app before your clock starts. No credit card is required to start.
Yes. Cal2Bill supports per-client rate overrides stored directly on your Zoho Books contact custom fields. Set a default rate in your settings, and override it for specific clients when needed — Cal2Bill picks up the right rate automatically.
Currently Cal2Bill is designed for one Outlook calendar account per Cal2Bill account — ideal for independent consultants and sole practitioners. Each person would need their own Cal2Bill subscription. Multi-user support is on the roadmap for a future version.
Cal2Bill adds a hidden tracking code like [EVT-a1b2c3d4] to each invoice line item description. This is how Cal2Bill recognises which calendar events have already been invoiced — preventing duplicates when you run Build Invoice again for the same client. Before sending your invoice to the client, click Clean & Send to strip these tags automatically. Your invoice will look completely professional with no trace of the codes.
Yes — but follow this order to avoid duplicates: rename the field in Zoho Books first, then update the matching field name in Cal2Bill Settings to match exactly. If you change the name in Cal2Bill Settings first, Cal2Bill will try to create a new field with the new name, leaving the old one behind. Existing invoices are never affected — only future per-client rate lookups.
If you need to control what number Zoho assigns to the next invoice — for example after deleting an invoice — open Zoho Books, click + New Invoice, then click the ⚙ cog wheel next to the invoice number field, enter your preferred next number, and click Cancel (not Save). Zoho will use that number as the starting point for the next invoice created, including drafts built by Cal2Bill.
You can cancel anytime from the Billing section inside the app. Your access continues until the end of your current billing period. Your settings and data are retained for 90 days after cancellation in case you return, then permanently deleted.
Cal2Bill never stores your calendar event contents, invoice line items, or client names. We store only what's necessary to operate the service: your authentication tokens, your billing rate settings, and your subscription status. Full details are in our Privacy Policy.
Absolutely — that's exactly the situation Cal2Bill was built for. You can scan up to several months of calendar history in one go. Cal2Bill's deduplication system tracks which events have already been invoiced, so you'll never accidentally double-bill a client even if you run it multiple times.
Troubleshooting

Something not working?

Check two things: first, the subject line of your Outlook event must contain the client's Display Name exactly as it appears in Zoho Books — though it is not case sensitive. Second, check that the event's Outlook category matches your billing label (e.g. "Onsite") and that it doesn't accidentally have an exclusion label on it such as "Paid" or "Invoice sent" — these cause events to be skipped automatically.
Per-client rate overrides are stored as custom fields on your Zoho Books contact. Check that the field names in Cal2Bill Settings match exactly what's in Zoho Books — including spacing and capitalisation. If they don't match, Cal2Bill falls back to your default rates silently. Also check that the client contact in Zoho actually has values entered in those custom fields.
Try disconnecting and reconnecting your Zoho account from Cal2Bill Settings. When the Zoho login page opens, make sure you are logged into the correct Zoho account and organisation. If you have multiple Zoho orgs, log out of Zoho completely first, then reconnect to ensure you connect to the right one.
Cal2Bill creates invoices as drafts — not sent invoices. In Zoho Books, go to Sales → Invoices and filter by status Draft. The invoice will be there waiting for your review before you send it to the client.
Cal2Bill only creates custom fields for rates that have an amount entered in Settings. If a rate field is left blank during onboarding, no Zoho custom field is created for it. Go to Settings, enter a rate amount for the field you need, and save — Cal2Bill will create the missing Zoho field automatically at that point.
Cal2Bill is optimised for Chromium-based browsers — Google Chrome, Microsoft Edge, Brave, and Opera. If you are experiencing issues, try switching to one of these. On Windows, Microsoft Edge is built-in and works perfectly. Avoid Internet Explorer entirely — it is not supported.
This happens when Build Invoice is run more than once without cleaning the draft first. Cal2Bill uses EVT tracking codes to detect duplicates, but if the draft was manually edited or the codes were removed, it may add items again. Click Clean & Send on the existing draft first to strip the tracking codes, then run Build Invoice again — Cal2Bill will correctly identify what's already there and only add new items.
Your 15-day trial starts on the day you build your first invoice — not when you create your account. If you set up your account and connected your apps but waited before building your first invoice, the trial clock only starts on that first build. If you believe there is an error, contact [email protected] and we will look into it.
Cal2Bill looks for custom fields by their exact name. If you renamed a field in Zoho Books without updating Cal2Bill Settings to match, Cal2Bill will not find it and will fall back to default rates. Go to Cal2Bill Settings, update the field name to match the new name in Zoho Books exactly, and save. Do not rename in Cal2Bill first — always rename in Zoho Books first, then update Cal2Bill to match.
Email us at [email protected] — we respond within one business day and we want to hear about it. Every reported issue helps make Cal2Bill better for everyone.
Support

We're here to help.

Have a question, found a bug, or want to explore a beta spot? Drop us a message and we'll get back to you — usually within one business day.

EMAIL [email protected]
BUILT BY Guido Derlagen — ITontheSpot, Toronto, Canada
RESPONSE Within 1 business day

🧪 Beta program open
Looking for 5–10 beta testers. Get 6 months free in exchange for honest feedback. Mention "beta" in your message.

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