Note: Only The Netherlands is covered by this information.

Keeping records is essential for avoiding issues with the Belastingdienst.

Even if you've followed all the rules, if the Belastingdienst questions you and you can't provide paperwork to back up your claims, you risk being hit with extra taxes, penalties, and interest.

What documents then should you preserve?

Records of income and sales

A breakdown of your total income, excluding the Service Fee for all the tasks you've performed on Taskhelper.

Expense or purchase records

Keep track of all of your business expenses, including cash purchases,  those for supplies, motor vehicle costs (fuel, maintenance, and repairs), and attire unique to your line of work. To keep track of small monetary expenditures, records might include receipts, invoices, credit card vouchers, and diaries.

You must keep a record of how you determined any private use of an item you acquired if it is used both for business and for personal purposes.

Year-end results

These consist of lists of those you owe money to (creditors) as well as those you owe money to (debtors).

Worksheets are also required to estimate the assets' declining worth (of which your car might be the main one). They are referred to as "depreciating assets." The best course of action may be to have your accountant create this computation for you because it can be complicated.

Bank statements

The documentation you get from the bank, this includes loan documents as well as bank and credit card statements.

Records for VAT on goods and services 

Tax invoices from your suppliers are the primary BTW documents you need to retain. To claim BTW credits, you need a tax invoice.

Don't forget to set aside time each week to update your records. This makes it easier to file your taxes because all the information is there and you aren't swamped with papers. This frees up time to concentrate on earning money rather than filling out paperwork.