Widowed parent’s allowance (WPA) is a regular payment for men and women bereaved before 6.4.17, who have at least one dependent child or ‘qualifying young person’ under 20 (see Chapter 39(1) ). It cannot be paid beyond pension age. You can only make a new claim for WPA if your spouse or civil partner has only recently been declared dead; you will need to confirm the cause of death. You must claim within 12 months of the date that the DWP decide that the death did occur before 6.4.17.
SSCBA, S.39A

WPA is taxable. WPA is included in the list of benefits to which the ‘benefit cap’ applies (see Chapter 15(10) and Box F.6 in Chapter 21).

Do you qualify? – The contribution conditions for WPA are the same as those for the basic state pension for people who reached pension age before 6.4.10 (see Box L.2 in Chapter 45, Disability Rights Handbook, 44th edition).
SSCBA, Sch 3 , para 5(2)&(3)

WPA will cease if you remarry, form a civil partnership or begin cohabiting