How to choose an offline invoice app

Offline should mean the whole invoice

An offline invoice app should let you open the client, add the work, calculate the tax, draw the PDF and prepare it for sending without a connection. A cached home screen is not enough. The useful test is whether you can finish the document in airplane mode.

That matters because the weakest signal is often where the paperwork starts: a basement plant room, a rural property, the back of a warehouse, or the road between one job and the next. Waiting until reception returns moves the invoice from the job you just finished into the pile of things you intend to do tonight.

Invoice Koi keeps the businesses, clients, prices, documents and numbering on the phone. Totals are calculated there and the PDF is drawn there. You can finish the invoice at the jobsite; sending it still needs whatever connection your mail or messaging app requires. AI, cloud backup and payment collection need an internet connection.

The honest offline test is simple: can you finish the PDF in airplane mode?

This is also why no account is required. A document that has to ask a server who you are before it opens is not an offline document, even if some of its fields were cached yesterday.

Seven things to test before choosing

Turn off the connection before you test, not after. Then test the parts that usually reveal where an app stops being local.

Also ask what happens to photographs. Invoice Koi stores receipt and job photographs on the device first. A subscription can carry those photographs to an account for backup, but losing the connection does not stop you opening the local copy or adding another one.

Card payment pages are different. A live payment needs a processor, so an app that promises payment processing cannot make that part offline. Koi can collect payments through Stripe while online. A payment made through a Koi payment link marks the invoice paid on its own. Cash, bank transfers and anything paid elsewhere, you record yourself. Recording one yourself carries no Koi fee.

Make the document before choosing the app

A feature list cannot tell you whether the finished invoice looks right. Make one, save the PDF, and read it at the size your customer will see.

The browser generator is the fastest test. It works on any device, asks for no account and puts no watermark on the page. It keeps the current draft in this browser when browser storage is available, but it is not a client directory or a backup. Save the finished PDF before clearing site data or moving to another device.

If the document is right and you make invoices regularly, the app adds the memory: clients, rates, the next invoice number, terms, tax and the estimate that becomes the bill. Setting up and drafting in it are free, so the workflow can be tested before you subscribe. Sending needs a subscription, with a free trial where your store offers one.