First of all, I want to congratulate you for actually shipping, and dare show it here on Hacker News.

However, I can't consider this an MVP. Sure it is minimal, but it is barely usable as it is right now. I'd like a datepicker, instead of writing the date by hand, and I'd like to be able to have a suggestion of tags I used in the past. I'd like to have the enter key submit the form. Such small details that would add great value.

Moreover, I expected the Day, Week, Month filter to show me only the expenses in that time frame, instead of just the total changing.

Keep it up! Very good job overall.