Hi Hun
I don't know about the NZ position but if your UK earnings would be subject to the following.
I would strongly suggest you do claim your allowable deductable expenses, as it sets a pattern for future claims at a time that you may be earning more and why pay more tax and national insurance than you are actually required to do?
You state you haven't kept a record of your earnings but if you have put all earnings into your bank your bank statement could be argued to be your record. A reasonable view has to be taken, the only record you could keep with a cash business such as ours is a hand written note and there isn't any back up evidence so surely your bank statements are your record. Think of a taxi driver, his record is his daily takings, OK he has further evidence of mileage but how much of that was non-business mileage? Or a market stall, they don't log down each sale they just take a note of the daily takings.
Anika Mae is correct in that you wouldn't need to submit these records unless the HMRC required you to do so. However, you need to get into the habit of keeping records to protect yourself as they can be requested at any time believe it or not they can even request to look at your records before you submit your tax return! but I think that is highly unlikely in our case.
I would strongly suggest that, in future, your self-employed earnings are all put thru' a separate bank account than your private one. After all if you are required to submit your self-employment records and you give them all your private bank statements they are likely to go on a "fishing expedition" through all your financial undertakings rather than just your business records. Even though you aren't doing anything you shouldn't you really don't want to give HMRC the opportunity to ask more and more questions, if you were paying an accountant and this happened your fees would be horrendous.
As for self-employment description, I would just use something vague, like therapist or adviser (some escorts like to put themselves done as beauticians etc).
Hope this helps but please remember the filing deadline (and tax payment due date) in the UK is 31st January (Monday) unless your return was submitted to you late but you would have been advised if you have a later filing date.
Hope this helps.
Adele xxx