So here OP has committed two separate offences - travelling without a valid ticket on the 8th only (please confirm that you have always held the correct ticket, not short faring etc except for this date), and refund fraud.
While Chiltern are one of the more difficult train companies to deal with, if you co-operate there is still a good chance they will offer you an out of court settlement. You should send a letter promptly to the Chiltern prosecutions department covering the following points:
- That you are sorry for what has happened and realise it is wrong, and that you understand public interest arguments against fare evasion (i.e. loses the taxpayer millions of £s/yr, etc);
- That you will not be doing it again (if convenient, take measures such as purchasing a season ticket to show commitment to travelling correctly)
- State that you would be very grateful if Chiltern would consider offering you an out of court settlement
If you do get a settlement, the amount will likely be:
- £150 or so admin fee
- Anytime Single for every journey where you have travelled with an invalid ticket or fraudulently refunded etc., undiscounted, without regard for fares paid
You want to calculate what this amount is, and start gathering the amount, as they will expect you to pay this amount in full promptly once the offer is received.
Alternatively, if you are prosecuted (likely under the railway byelaws - I don’t know what they would use for fraudulent refunds, presumably this doesn’t rise to the level where the TOC would consider it worth the effort to pursue a Fraud Act prosecution), there will be:
- A court fine based on your income (or £120/wk whichever is greater) with a discount if a guilty plea is entered early
- Requirement to pay back losses incurred by the TOC, with 40% surcharge
In addition you will receive a criminal conviction, which is non-recordable and does not normally show on DBS checks, but your employer may require you to disclose any convictions you receive.