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1.15Under Standing Order No 9, any vacancy arising as a result of the death, expulsion or resignation of one of the 90 hereditary peers elected under the House of Lords Act 1999 must be filled by means of a by-election. By-elections are conducted in accordance with arrangements made by the Clerk of the Parliaments and take place within three months of a vacancy occurring. If the vacancy is among the 75, only the excepted hereditary peers (including those elected among the 15) in the relevant party or group are entitled to vote (Standing Order No 9(6)). If the vacancy is among the 15, the whole House is entitled to vote (Standing Order No 9(7)).

The Clerk of the Parliaments maintains a register of hereditary peers who wish to stand in any by-election under Standing Order No 10. Any excluded hereditary peer is entitled to be included in the register, not just those who were previously Members of the House. Under Standing Order No 10, any hereditary peer not previously in receipt of a writ of summons who wishes to be included in the register petitions the House, and any such petition is referred to the Lord Chancellor to consider and report upon whether such peer has established their right to be included in the register (see also para 11.6 ).