A couple of points:
As you probably know, ages recorded at death weren’t always accurate, so best to be a bit flexible when searching for deaths.
If William was dead at the time of the 1871 census, you might expect Mary to be “widow” rather than wife, though these things weren’t set in stone.
If you give us some more details of your family eg census references, dates and places of birth, children etc we might be able to help further.
Thanks - its a bit convoluted so bear with me!
William Dawson b.08/12/1822 in Newcastle married Mary Dean (b.1824) on 01/05/1843 in Newcastle.
At that point, he is a Grocer, but then appears to join Durham Police and moved around Durham having several children. In 1851 the family are living in Gateshead, and a police officer, but in 1861 they now live in Birmingham and he is a painter/glazier.
What starts to complicate matters is when his son Richard gets married in Liverpool in 1870, his father is listed as Charles Dawson. The 1871 Census has the family in Liverpool without William, and then there are several marriages in 1872 where father is listed as Charles William Dawson, and then William Charles Dawson.
So its a lot of movement - Newcastle, several locations around Durham, Birmingham, and then Liverpool, and suddenly this variant name Charles cropping up.
1861 Census -
Tennant Street, St Thomas, Birmingham: William Dawson 39:1822 (Painter and Glazier) b. Newcastle, wife Mary Dawson 37:1824, b. Newcastle, sons Richard William Dawson 12:1849 b. Gainford, Thos H Dawson 11:1850 b. Darlington, Durham, Louisa Dawson 8:1853 b. Gateshead, Eliza. Dawson 5:1856 b. Bishops Auckland, Wm Dawson 9 months:1861 b. Birmingham.
1870 Marriage Cert – Richard John Dawson (Artist) of South Hill Road, Liverpool, and Sarah Jane Hewitt of South Hill Road married. Fathers are Charles Dawson (Painter) and Thomas Hewitt (Shipwright). Sister Louisa Dawson is a Witness.
1871 Census -
Iden St, West Derby, Liverpool: Mary Dawson 48:1823 (Head) b. Northumberland, Thomas H Dawson 21:1850 b. Co Durham, William 10:1861 b. Warwickshire.
1872 Louisa Dawson married to Henry Martin in West Derby. Father recorded as Charles William Dawson, a Painter. Not shown as deceased, although Henry Martin’s father is. Thomas Dawson is a witness.
1872 Thomas Dawson is married in Liverpool, Father shown as Charles William Dawson, a Painter. Eliza is present as a witness.
1877 Elizabeth Dawson married to a ships steward where father is recorded as William Charles Dawson, deceased.
1881 Census - no sign of Mary Dawson or Thomas H Dawson (believe he emigrates to US in 1880).
So my aim is to narrow down timeframes of death for William/Charles from 1861-1877 and Mary Dawson from 1871 - 1881 to something a bit more practical as the names are common, and I cannot see any clear deaths in places they are associated with.