HMRC - Real Time Information (RTI) - Producing the cross reference hash

The strategic RTI solution is to use the Bacs channel to send both the payment file and the RTI data. However, during the consultation process there were significant concerns about the time table. HMRC have created an interim solution so the RTI data will be sent through existing Internet or EDI channel. The payment will be sent through Bacs. To bring the data back together HMRC will use the hash.

Who will produce the cross reference hash?

Payroll software will be responsible for producing the cross reference hash. Payroll software developers will need to upgrade their software and their interface to the Bacs transmission software. When the payroll software passes information to the Bacs Software in preparation for submission to Bacs, it will need to include the four character random string. The Bacs software will then build the random string into field 7 of the Standard 18 file.

How is the hash constructed?

The hash is constructed from the 4 character random string, sortcode of the originators bank, the sortcode of the recipients bank, the amount of the payment in pence. A 256 bit Secure hash algorithm (SHA-256) is used to produce the hash.

To read HMRC paper on production of the cross reference hash click here
To read the latest consultation paper published by HMRC click here