Used to be that TA membership was deemed as preventing you getting a job, the changes in 1986 meant that you could claim benefits and be in the TA at the same time.
That changed when a certain G Brown became Chancellor of the Exchequer and the benefits had to be deducted on a pound per pound basis to the value of the TA pay. So a normal attender would be effectively working for nothing. However as with all of his other great ideas it was made very complicated involving copious form filling, presumption of future earnings and actual deductions based on those presumptions, and a cloying layer of bureaucracy trowelled on the top.
Needless to say the opportunity for someone to move from unemployed scrounger to tax paying (soldier) citizen via some time in the the TA was removed and social mobility stymied again. I saw two lads from my intake change from unemployable, unqualified admin nightmares into adequate squaddies before joining the reqular army via the local recruitment office.
As MSR says this is CRR job and a point I've made to a number of 1*s in person whenever they've regurgitated the statistic that 50% of the TA are on the dole. To be fair the then most senior TA soldier was aware of the actuality and was equally frustrated.
The short version, from my recent experience, is that it's a bag of arrse mess, and unless you have some compelling reason to be registered unemployed (as opposed to merely not working), stay off the dole and do as many days as you can. Anyone who can swing 6-7 days a month will come out ahead anyway.
I've heard of people slightly lying about the dates they turned up at TA, i.e. if you did 6 days within a month they'd all be put down as working for a continuous week - so you loose benefits for a week. Plus reclaiming the tax makes it a double bounty year