Mobile App Developer. Taxes from App Revenue

[Big Bounty]

If a tax resident of Finland wants to start making paid mobile apps (e.g. App Store) as a hobby, what would be the best strategy to minimize taxes and the amount of paper work? We’re talking about a small revenue here, maybe a 100€/month by the end of the first year.

AFAIK there’s no need to register a business if the revenue is less than 8500€/year and a private individual can legally do it if their profits are declared and paid taxes from (once a year). Is this correct? What % of taxes should one expect to pay from the earnings of this magnitude? What happens if the business grows faster than expected and in some year it overreaches the 8500€ boundary?

Also, I heard that if the revenue is less than a certain threshold (400€/month, I guess) then it’s not taxable. Is this true?

I’d appreciate any help! And even if you don’t know the exact answers but can point me to the related legal documents, that’d be great!

[betelgeuse]

AFAIK there’s no need to register a business if the revenue is less than 8500€/year and a private individual can legally do it if their profits are declared and paid taxes from (once a year). Is this correct? What % of taxes should one expect to pay from the earnings of this magnitude? What happens if the business grows faster than expected and in some year it overreaches the 8500€ boundary?

The VAT limit is 10k a year. If you go over the limits, you are liable for the whole sum. This means it's not a good idea to go over the limit when not registered. However, it's possible to register even if under the limit (the collected VAT will just not be collected and considered taxable income).

Personal income is taxed progressively so it's impossible to to answer about the percentage without the full picture.

Also, I heard that if the revenue is less than a certain threshold (400€/month, I guess) then it’s not taxable. Is this true?

The lowest income tax brackets are zero. It still has to be declared.