A government brief released under freedom of information laws showed Ms Burch asked for new legislation to be drafted to allow $50 notes in ACT poker machines, along with a $500 cash limit as a harm minimisation measure.

But when the advice, sent on December 11, showed the cost of implementing $500 cash limits would be very high, Ms Burch rejected advice suggesting an opt-in scheme and wrote for $50 note acceptors to be progressed immediately without it.

"The cost of introduction of $500 limit is prohibitive," she wrote on the brief.

"However I [am] also keen to continue to explore harm minimisation so please draft separate instrument for $500 limit. This [is] then to be considered following further advice on reducing costs of implementation.

"Progress instrument for $50 note acceptor now."

A spokeswoman for Ms Burch said she had already accepted the error in uncoupling the $50 note acceptor from the cash input limit.

The documents show Ms Burch had asked for the new laws to be in place by the end of the 2014.

The Canberra Times revealed in January the ACT government had quietly legislated to allow $50 notes in Canberra poker machines.

In the resulting controversy, the new laws were struck down and Ms Burch was reprimanded by chief minister Andrew Barr.

The government brief was mentioned in emails from Ms Burch's former chief-of-staff Philip Tardiff and Clubs ACT chief executive Jeff House in December, in which Mr House described the new laws as a "very welcome Xmas present".

Public servants advised the decision to allow $50 notes in poker machines was potentially diluting the ACT's harm minimisation framework protecting problem gamblers, adding community organisations would possibly raise concerns.

"For this reason, a cash input limit of $500 will also be introduced simultaneously to mitigate risk to problem gamblers as a result of the change," the advice said.

"The cash input limit will apply to all denominations excluding $100 notes in machines that have upgraded to $50 note acceptors. The cash input limit will operate as a maximum limit."

But the government found while changing poker machines to accept $50 notes was simple, adding the $500 cash limit was complex as it needed software changes on machines..

These would require each supplier to amend the software of each game/machine and resubmit it for testing and approval in NSW.

The department estimated to convert all 704 games in the territory would cost $3.5 million, with possible additional costs to suppliers.

The brief suggested Ms Burch might want to consider making the $500 limit an "opt-in" scheme for clubs, given the complexities and cost of converting machines.

If they chose to bring in the cash limit they could also allow $50 notes in machines; if not, they would have to stick to a maximum of $20 notes.

Ms Burch's spokeswoman said the minister was on the record has accepting the error in uncoupling the $50 note acceptor from the cash input limit.

"As you can see from the notations on the advice dated December 11, 2014, the cost involved in implementing the input limit was prohibitive, hence the minister sought further advice on mitigating the cost of implementation of the input limit," she said.

The spokeswoman said the minister had recognised the lack of an input limit in an earlier brief, which had led her to ask for the Directorate to proceed with both the note acceptor and a cash input limit.

with Markus Mannheim