Ive been self employed for a couple of years but only got into escorting last year. I record every thing - date of booking, duration, website they found me on as well as my income and outgoings.
Outgoings are only for things like rent that I pay for my incall place or hotels. I dont add smaller items like lube, condoms because as a 'cash basis', you can only add items that last at least 2 years.
Just like Adele, I have a spreadsheet that auto calculates the monthly expenses/earnings (Apr - Mar), then at the end theres an amalgamation of the months income/outgoings so I can see how much Ive made for the whole year