According to the official Guidance for Tier 1: http://www.ukba.homeoffice.gov.uk/sitecontent/applicationforms/pbs/t1-general-guidance.pdf
3. See Page 20 item 100:
The applicant can claim points for: previous earnings in any single, consecutive 12-month period during the 15 months immediately before the date of applying. An applicant may claim points for a 12-month period of earnings outside of this 15 months if they can show that he/she has been:
away from the workplace for a time during • the last 12 months because of a period
Further information can be found in Appendix A of the Immigration Rules (table 2 and paragraphs 8 -23).
which can be found here: http://www.ukba.homeoffice.gov.uk/policyandlaw/immigrationlaw/immigrationrules/appendixa/.
13. Earnings include, but are not limited to:
(a) salaries (includes full-time, part-time and bonuses),
(b) earnings derived through self-employment,
(c) earnings derived through business activities,
(d) statutory and contractual maternity pay, statutory and contractual adoption pay,
(e) allowances (such as accommodation, schooling or car allowances) which form part of an applicant's remuneration package,
(f) dividends from investments, where it is a company in which the applicant is active in the day-to-day management, or where the applicant receives the dividend as part of their remuneration package,
(g) property rental income, where this constitutes part of the applicant's business, and
(h) payments in lieu of notice.
14.Where the earnings take the form of a salary or wages, they will be assessed before tax (i.e. gross salary).
15. Where the earnings are the profits of a business derived through self-employment or other business activities, the earnings that will be assessed are the profits of the business before tax. Where the applicant only has a share of the business, the earnings that will be assessed are the profits of the business before tax to which the applicant is entitled.
16. Earnings do not include unearned sources of income, such as:
(a) allowances (such as accommodation, schooling or car allowances) which are paid as reimbursement for monies the applicant has previously paid,
(b) dividends from investments, unless it is a company in which the applicant is active in the day-to-day management, or unless the applicant receives the dividend as part of their remuneration package,
(c) property rental income, unless this constitutes part of the applicant's business,
(d) interest on savings,
(e) funds received through inheritance,
(f) monies paid to the applicant as a pension,
(g) expenses where the payment constitutes a reimbursement for monies the applicant has previously outlaid,
(h) redundancy payment,
(i) sponsorship for periods of study,
(j) state benefits, or
(k) prize money or competition winnings, other then where they are directly related to the applicant's main profession or occupation.
17. Earnings will not be taken into account if the applicant was in breach of the UK's immigration laws at the time those earnings were made.
1 & 2: So to me looks like bonuses count, but severance (redundancy pay) does not.