# Onyx IX CSS vs Simple Invoice Maker

The clearest difference is in-app purchases: Onyx IX CSS at none against Simple Invoice Maker's 4. Onyx IX CSS also leads on iOS requirement (13.0 vs 16.4). Simple Invoice Maker's advantage is update cadence (every 3 weeks vs every 4 months). On price, ads and device support there is nothing between them.

Both are free to download. Simple Invoice Maker sells 4 in-app purchases, starting at $4.99 per 7 days. Onyx IX CSS asks for nothing beyond the download.

Onyx IX CSS ships an update every 4 months, Simple Invoice Maker every 3 weeks. The most recent releases landed on September 18, 2026 and June 9, 2026 respectively.

## The numbers

| Metric | Onyx IX CSS | Simple Invoice Maker |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[4.8 (11 ratings)](https://appshunter.io/ios/app/simple-invoice-maker-invo/id6478788721/reviews)** |
| Number of ratings | — | **11** |
| Positive reviews | — | 100.0% of reviews |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 4 months | **Every 3 weeks** |
| Monetization | — | Free with in-app purchases |
| Size | 27 MB | 46 MB |
| Requires iOS | **13.0** | 16.4 |
| Devices | iPhone, iPod | iPhone, iPad |
| Age rating | 4+ | 17+ |
| Developer | [Ultimate Solutions](https://appshunter.io/developer/1190319655) | [Hypex Mobile](https://appshunter.io/developer/1773535682) |

## What reviewers say

### Onyx IX CSS

[App page](https://appshunter.io/ios/app/onyx-ix-css/id1584092874)

**Features:** macOS Compatibility

**In-app purchases:** none


### Simple Invoice Maker

[App page](https://appshunter.io/ios/app/simple-invoice-maker-invo/id6478788721)

Create professional invoices, estimates, and receipts quickly and easily. Customize your documents with your logo and brand colors, and share them instantly via email or messaging apps. This app simplifies billing for businesses and freelancers worldwide.

**Highlights:** Fast invoice creation, Add logo and signature, Share via WhatsApp and email, Customizable colors, Global compliance, Secure data encryption

**Features:** macOS Compatibility

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Premium | $4.99 | per 7 days |
| Weekly Subscription | $4.99 | per 7 days |
| Monthly Subscription | $8.99 | per month |
| Annual Subscription | $34.99 | per year |


## Frequently asked questions

### Is Onyx IX CSS free?

Onyx IX CSS is free to download, with no in-app purchases.

### Is Simple Invoice Maker free?

Simple Invoice Maker is free to download, with in-app purchases available.

### Do Onyx IX CSS or Simple Invoice Maker have ads?

Neither Onyx IX CSS nor Simple Invoice Maker shows ads.

### Which is updated more often, Onyx IX CSS or Simple Invoice Maker?

Onyx IX CSS ships an update every 4 months, and Simple Invoice Maker every 3 weeks. Most recently, Onyx IX CSS was updated on September 18, 2026 and Simple Invoice Maker on June 9, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*