Below Betair Minimum Bets (API Change as of 18th June 2020)

[TheBetEngine]

Betfair implemented an unannounced, retrospective change to the API on the 18th June 2020 which has a direct effect on the placement/acceptance of below-Betfair-minimum bets.

Basically, this change has been made to prevent people from exploiting a loophole that exists on the rounding of profits received from winning bets.

The change has affected all third-party applications. Betfair gave zero notice of the change and zero details of what had changed!

Today, Betfair finally posted up some vague technical details of the change:

Any bets that are placed to benefit from rounding will now be rejected with the error INVALID_PROFIT_RATIO

Please see further information and example below:

If customers attempt to place a bet (including a bet used a size-up edit or price change) or cancel a bet down to a remaining size, such that it returns 20% less or 25% more than it ‘ought’ to, that bet will fail with an INVALID_PROFIT_RATIO error returned to API customers – (customers attempting such on the Betfair website or mobile app will receive a generic error).

For example – a 13p @ 1.06 back bet is ‘unfair’ as it ‘ought’ to win 0.78p, but actually - due to rounding - wins 1p, a 28% uplift.

So attempting to:

• Increase the size of a £2.00 bet @ 1.06 to £2.13 (which creates a new 13p bet @ 1.06)
• Cancel £1.83 of a £2.00 bet @ 1.06 (to leave a 13p remainder @ 1.06)
• Price-editing a 13p @ 1000 bet to 13p @ 1.06 (which cancels the bet @ 1000 and creates a new one @ 1.06)

Will all fail with the error above.


Counteracting this will require a change to TheBetEngine. This will be implemented and released as soon as possible.

[TheBetEngine]

Whilst we wait for Betfair to confirm all of the changes and to determine how to work around the issue, the following may prove useful:

• If you are backing then please ensure that you have turned OFF Maximise Chances on the General/Options tab.

• If you are laying, then please refer to viewtopic.php?p=2600#p2600

[TheBetEngine]

I have uploaded a test release that introduces a fix for the below-Betfair-minimum issues introduced by Betfair last Friday.

If you are using below-Betfair-minimum bets and wish to try out the new software then you can download and install it from http://www.thebetengine.co.uk/downloads ... 9.5.7D.exe

Further changes are possible so this version will not be pushed out as an automatic upgrade until testing is complete.