Help with tax code

[Sausagesonlegs]

My DM is a widowed pensioner (state pension + small private pension). Her tax code is S81L. We cannot work out what this code represents. I know S is for Scottish tax. I couldn't find explanation on gov website. Anyone explain it in a nutshell?

https://www.tax.service.gov.uk/guidance/get-help-understanding-your-tax-code/start/where-do-you-live

this page should help, you enter the tax code and then how much she receives in pension payments, it’s pretty self explanatory

It means her tax free allowance is £810 per year. Anything over and above that she will pay tax on.