What the law requires
Regulation (EC) No 852/2004, Annex II, Chapter I requires cold storage in which food temperatures can be monitored and, where necessary, recorded, and Chapter IX says the cold chain must not be interrupted. Article 5 of the same regulation asks for HACCP records that fit the size of the business, and Regulation (EC) No 2073/2005 sets microbiological criteria for some chilled foods, for example Listeria in ready-to-eat food. In the UK, the Food Standards Agency pack Safer food, better business asks for the same kind of fridge and freezer checks. The limits and how often you check come from your own HACCP plan and the national guide.
Write the limits from your HACCP plan at the top of the sheet. They depend on the food and on the rules in your country. If a value is out of range, record what you did in the corrective action log.