If you provide payslip for 60k and play 100/month, there most probably are no further questions.
No, I know, and thats why the system fails.
In my example above there would be £12k a year left over, take off say half for food, clothes and entertainment, leaves say £6k, £500 a month.
I could deposit £100 a month at 10 casinos, can't afford that. But working from a payslip no casino would ever know.
If they are serious about this, there should be a central agency to deal with SoW checks, it set a limit, have a database like gamstop, all casinos send details of deposits and withdrawals, and the agency send a yes/no response as to if someone can deposit. Otherwise its useless, and we get situations like Casumo who make things nigh on impossible for people to comply.
So, say the agency set an affordability amount of £5k a year. Someone deposits £3k over 10 casinos in 6 months, they only have £2k left. However, if they win £8k, thats added back and the limit is then £10k they can deposit. The advantage for players is that they only have to do it once, and you don't get dodgy casinos refusing withdrawals as you can't supply a bank statement and passport from someone you sold something to on ebay 18 months ago. The advantage for casinos is that they don't have all the extra work, and angry customers.
Thats the only effective way I can see SoW being carried out properly.