Expense tracking on mobile: how not to lose a receipt and keep your costs under control

Every business owner knows the feeling — you're digging through pockets, wallets, and drawers full of crumpled receipts, trying to piece together last month's expenses. Some receipts fade, others disappear, and you end up losing legitimate costs you could have deducted from your taxes.

Yet the solution is literally in your pocket. Your mobile phone can be your best tool for tracking expenses. In this article, we'll show you how to track expenses effectively on your phone, whether digital copies of documents are legally valid, and how to automate the whole process as much as possible.

Why paper receipts aren't enough

The problem with thermal paper

Most till receipts are printed on thermal paper, which has a limited lifespan. On average, the text starts fading within 6–12 months, and after 2–3 years the receipt can become completely illegible. Yet the legal requirement for archiving tax documents is:

• Tax records: documents must be kept for as long as the right to assess or reassess tax has not lapsed (typically 3 years from the end of the filing deadline)
• Accounting records: accounting documents are kept for 5 years starting from the end of the accounting period they relate to
• VAT documents: 10 years from the end of the tax period in which the transaction took place

Loss and damage

Surveys suggest that the average business owner loses 5–10% of their receipts each year. For a self-employed person with monthly expenses of 30,000 Kč, that can mean losing costs worth 18,000–36,000 Kč annually. At a tax rate of 15%, you'd be needlessly overpaying tax by 2,700–5,400 Kč.

The time cost of manual sorting

Manually sorting paper documents takes the average business owner 3–5 hours per month. That's time you could be spending on your business — or on yourself.

Are digital copies of receipts legally valid?

This is the key question every business owner asks before they start photographing receipts. The answer is: yes, under certain conditions.

What the law says

The Accounting Act (No. 563/1991 Coll.) in its current form permits accounting records to be kept in a technical format. This includes digital copies of originally paper documents. The key conditions are:

1. Legibility: The digital copy must remain legible throughout the entire archiving period
2. Authenticity of origin: The origin of the document must be verifiable
3. Integrity of content: The content of the document must not be altered
4. Availability: The document must be accessible for inspection purposes

The VAT Act and electronic documents

The VAT Act (No. 235/2004 Coll.) explicitly recognises tax documents in electronic form. The condition is that the authenticity of origin, integrity of content, and legibility of the document are ensured from the moment of issue until the end of the retention period.

How to ensure a digital copy is valid

• Sufficient photo quality — the entire receipt must be legible, with no blurring
• Preserving metadata — the date and time the photo was taken serves as evidence
• Systematic storage — ideally in a system that prevents subsequent alterations
• Backups — in at least two independent locations

How to photograph receipts properly with your phone

The quality of the photo determines whether the digital copy will be usable. Follow these guidelines:

Technical requirements for the photo

Resolution: At least 5 megapixels (practically every modern smartphone meets this).

Lighting: Photograph in a well-lit area. Avoid direct sunlight, which creates glare, and environments that are too dark.

Sharpness: Wait for the camera to focus. Most phones focus automatically — just give it a moment after pointing the camera.

Angle: Shoot straight down from above, not at an angle. This prevents text distortion.

Full document: The photo must show the entire receipt, including the header (seller's name, company registration number) and footer (total amount, date, time).

Special cases

Long receipts (e.g. from wholesale stores): Some apps let you photograph multiple sections and combine them. Alternatively, take two photos — the header with line items, and the footer with the total.

Receipts on glossy paper: Avoid direct lighting when shooting, as it creates glare. Tilt the receipt slightly or adjust the angle of your light source.

Very small receipts (from vending machines, parking meters): Use the macro function or zoom on your camera. Get close — around 10–15 cm away.

Methods for mobile expense tracking

Method 1: A folder in your photo gallery

The simplest approach — create a folder called "Receipts" in your phone's gallery and save all receipt photos there.

Pros: No extra app needed, instant capture. Cons: No automatic sorting, manual data entry required, risk of accidental deletion.

Method 2: Notes or a spreadsheet

Alongside each photo, you manually record the details in your phone's notes app or in a cloud-based spreadsheet (Google Sheets, Excel Online).

Pros: Better organisation, ability to filter. Cons: Time-consuming, double effort (photographing + typing).

Method 3: A dedicated app

There are many apps for scanning and recording documents. These typically offer OCR (optical character recognition), automatic extraction of key data, and data export.

Pros: Automation, clear overview, export functionality. Cons: Another app on your phone, often paid, requires learning a new interface.

Method 4: AI assistant via WhatsApp

The newest approach — you photograph a receipt and send it via WhatsApp to an AI assistant, which processes it automatically. No new app, no complicated interface.

Pros: Zero learning curve, works through an app you already have, instant processing. Cons: Requires an internet connection.

Expense categories you need to track

Correct categorisation is essential for accurate tax record-keeping. Here are the most common categories for the self-employed:

Materials and goods

• Raw materials for production
• Goods for resale
• Office supplies
• Consumables

Services

• Phone and internet
• Hosting and software
• Accounting and legal services
• Postage and courier services

Travel and transport

• Fuel
• Parking
• Public transport
• Motorway vignette

Operating costs

• Office or premises rent
• Utilities (electricity, gas, water)
• Insurance
• Maintenance and repairs

Entertainment (partially deductible)

• Refreshments at business meetings (not tax-deductible, but important to record for VAT purposes)
• Small gifts for clients

Digital documents vs. paper — what to archive

When a digital copy is sufficient

• Standard till receipts
• Simplified tax documents (up to 10,000 Kč)
• Internal documents

When you should keep the original too

• Contracts with signatures (until you have a digital signature)
• Property-related documents
• Documents for significant investments
• Payroll documents (if you have employees)

How to organise your digital archive

Create a clear folder structure:

Expenses/
├── 2026/
│   ├── 01-January/
│   ├── 02-February/
│   ├── ...
│   └── 12-December/
├── 2025/
└── ...

Within each month, name files in a clear, consistent way: 2026-02-15_Alza_notebook_24990.jpg

The most common mistakes in expense tracking

1. Putting it off until later

The worst thing you can do is pile up paper receipts and tell yourself "I'll deal with it at the end of the month." By the end of the month, you'll have a mountain of documents — some illegible, others missing. Record things immediately.

2. Incomplete documents

A receipt without the seller's registration number or without a date is not a valid tax document. Always check when making a purchase that the receipt includes the required details. For purchases over 10,000 Kč, request a full tax invoice.

3. Mixing personal and business expenses

If you buy both business and personal items on a single receipt, you need to clearly separate the business expenses. Ideally, make separate purchases.

4. Not recording small expenses

Parking for 50 Kč, postage for 100 Kč — they seem insignificant, but they add up to thousands of crowns over a year. Record everything.

5. Miscategorising expenses

Putting an expense in the wrong category can cause problems during an inspection. Set clear categorisation rules for yourself and follow them consistently.

Required details on a tax document

For an expense document to be recognised, it must contain certain mandatory information. When photographing a receipt, check that all of these are visible.

Simplified tax document (up to 10,000 Kč)

• Identification of the party making the supply (name, company registration number, VAT number)
• Document reference number
• Date of issue or date of the taxable supply
• Scope and subject of the supply
• Total price including VAT
• VAT rate, or a statement that the supply is exempt

Full tax invoice (over 10,000 Kč or on request)

Additionally includes:

• Identification of the recipient (your name, company registration number, VAT number)
• Tax base and VAT amount shown separately

How DokladBot handles mobile expense tracking

DokladBot is an AI accounting assistant that works via WhatsApp and transforms the way self-employed people track their expenses. Instead of complex apps and manual data entry, all it takes is one step — photograph the receipt and send it via WhatsApp.

How it works in practice

1. You receive a receipt — in a shop, a restaurant, at a petrol station
2. You photograph it with your phone
3. You send the photo to DokladBot via WhatsApp
4. DokladBot automatically identifies: the supplier, date, amount, and individual line items
5. It categorises the expense correctly
6. It saves the document to your digital records

The whole process takes less than 15 seconds. No typing, no complex forms, no new app to learn.

Why this approach is more effective

• Immediacy: You record the document the moment you receive it. No putting it off.
• Accuracy: AI recognition minimises errors from manual data entry.
• Accessibility: You always have WhatsApp to hand, unlike accounting software.
• Overview: You can request a summary of expenses for any period at any time.

Try DokladBot and forget about lost receipts — your AI accounting assistant that works wherever you are. On WhatsApp.

Backing up and securing digital documents

The 3-2-1 rule

For safe storage of digital documents, follow the 3-2-1 rule:

• 3 copies of your data
• 2 different types of storage (phone + cloud, or cloud + external drive)
• 1 copy in a separate location (cloud storage)

Recommended cloud services

• Google Drive (15 GB free)
• OneDrive (5 GB free, 1 TB with Microsoft 365)
• iCloud (5 GB free)

Automatic photo backup

Enable automatic photo backup to the cloud. Most phones support this natively:

• Android: Google Photos with automatic backup
• iPhone: iCloud Photos

Frequently asked questions (FAQ)

Can I throw away the paper receipt after photographing it?

The law does not require you to keep the paper original if you have a reliable digital copy. However, for high-value documents or important contracts, we recommend keeping the paper original at least until you've verified the quality of the digital copy.

How long do I need to keep digital copies of documents?

The same length of time as paper originals. For tax record-keeping, at least until the deadline for tax assessment has passed (typically 3 years from the date of filing your tax return). For VAT-registered businesses, 10 years. For businesses keeping full accounts, 5 years.

Is a screenshot of an invoice from an email sufficient?

Yes, but we recommend downloading and archiving the full PDF file if the invoice is in PDF format. A screenshot may be lower quality and won't contain the metadata of the original file.

What if the tax authority refuses to accept my digital copy?

In practice this is very rare, as long as the copy is good quality and legible. The tax officer may ask you to prove the authenticity of the document's origin — which is why it's important to use a system with timestamps and a history log.

Do I need to track expenses if I use flat-rate expenses?

If you claim expenses as a percentage of income (flat-rate expenses), you don't need to keep individual expense documents. Tracking income alone is sufficient. However, if you are VAT-registered, you must also track expenses in order to claim input VAT deductions.

What resolution is sufficient for a photo?

For a standard receipt, a resolution of 3–5 megapixels is enough, provided the photo is sharp and well-lit. Sharpness and legibility of the text matter more than raw resolution.

Can I record expenses from previous months retrospectively?

Yes — what matters is that the document corresponds to the actual date of purchase. The photo can be taken at any time, as long as the receipt is still legible. That said, the sooner you record a document, the better.

Do I need to keep records of card payments if I have bank statements?

A bank statement proves that a payment was made, but not what was purchased. For accurate record-keeping, you also need a document showing the breakdown of items — especially if you want to categorise expenses correctly and claim VAT deductions.