| Postcode | Country | County | Type | Status |
|---|---|---|---|---|
| England | Hertfordshire | Large | Terminated December 1998 | |
| England | Hertfordshire | Large | Terminated December 1992 | |
| England | Hertfordshire | Small | ||
| England | (pseudo) England (UA/MD/LB) | Small | ||
| England | Hertfordshire | Small | ||
| England | Hertfordshire | Small | ||
| England | Hertfordshire | Small | ||
| England | Hertfordshire | Small | ||
| England | Hertfordshire | Small | ||
| England | Hertfordshire | Large | Terminated March 2004 | |
| England | Hertfordshire | Small | ||
| England | Hertfordshire | Small | ||
| England | Hertfordshire | Small | Terminated April 2020 | |
| England | Hertfordshire | Small | ||
| England | Hertfordshire | Small | ||
| England | Hertfordshire | Small | ||
| England | Hertfordshire | Small | ||
| England | Hertfordshire | Small | ||
| England | Hertfordshire | Small | ||
| England | Hertfordshire | Small |