This report drawn up by the UK Office of Fair Trading, and examining banking practice in other countries such as NZ and Canada, refers to the "MICR codeline":

http://www.oft.gov.uk/shared_oft/reports/financial_products/...

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Note added at 1 hr (2007-04-04 23:42:45 GMT)
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Thanks for pointing that out. If MICR is out, then maybe just "codeline" or "code line":

The Newsletter of the Cheque Printer Accreditation Scheme ... Attempts to read the printed code line on all. documents whether in OCR or MICR print. ...
www.apacs.org.uk/resources_publications/documents/ChequeMat...

design of cheque, use of Code Line, use of cheque and other documents to be ... embossed printing, or any mark readable for MICR E13B or OCR E13B Reader, in ...
www.bot.or.th/BOTHOMEPAGE/BankAtWork/Payment/Rules/E_Std_Ch...

The cheque 1 contains two fields, a first field 2 with an E13B character code line 4 and a second field 3 with an OCR character code line 6. ...
www.freepatentsonline.com/4584703.html

UK4, UK Euro Corporate cheque gauge, £30.00. UK5, UK Credit gauge with full MICR codeline, £30.00. UK6, UK Credit gauge with full OCR codeline, £30.00 ...
www.checksystems.com/alinment.htm