I am self employed. My country allows me to declare flat expenses on up to 60% of my income. No accounting or proof needed. Real taxation is around 20% on $100K income (including social and health insurance).

So every year I spend about 2 hours with:

- sum all money that arrived to my account in last year

- fill form on IRS website

- update standing orders for health/social contributions for the next year

- one month latter, ring IRS and other offices, just to check all went through

If you move every two months, I would not worry about it too much. Important is:

- you pay taxes somewhere (preferably in your home country)

- you do not work for locals