(this is the closest StackExchange site I could find, even so, I'm sorry if the Q is still a bit out of place).
So, I've just finished building an application for better handling some of my needs and responsibilities. Eg. I have a billing module for issuing invoices, keeping records of my finances, etc. This software is solely for my own personal use, there is no way I will ever give anyone access or source codes to run their own instances. Now, the backbone of this software is obviously a comprehensive database with such records as people and companies.
And I wonder, how legal this technically is? This database obviously contains a lot of personal information/data, information entered exclusively by me. This information is accessible only by me, it's not and will not ever be used for any commercial purposes (I won't ever sell the information itself, nor the information metadata).
So, am I technically breaking any laws/regulations just by having such software?
For instance, intuitively it seems to me that having a directory with people, their phone numbers, emails, addresses, etc. clearly breaks GDPR rules. However, on second thought, this is precisely what the contacts app on my phone is - a directory of people with their personal information. So is this the same thing, or does the exact same concept break different rules when it's implemented in the phone vs. custom software?