Table 3: Linkage stage 2: 7 step deterministic algorithm for linking the personal demographic service to hospital episode statistics.

Step	NHS number	Date of birth	Sex	Postcode*
1	Exact	Exact	Exact	Exact
2	Exact	Exact	Exact
3	Exact	Partial	Exact	Exact
4	Exact	Partial	Exact
5	Exact			Exact
6		Exact	Exact	Exact
	Where NHS number does not contradict the match and date of birth is not 1 January
7		Exact	Exact	Exact
	Where date of birth is not 1 January

Notes: * Full postcode (e.g. LS0 0AA). Exact refers to exact linking; Partial refers exact linking but using month and year of birth only.