Update `allowance()` documentation

[Mark-Eis]

Fiscal/man/allowance.Rd

Line 12 in e22ac22

allowance(taxable, deficit = NULL, opts = tax_opts())

allowance(taxable, deficit = NULL, round10 = TRUE, opts = tax_opts())

Fiscal/man/allowance.Rd

Line 19 in e22ac22

\item{opts}{options, as created by \code{\link{tax_opts}()}, see details.}

  \item{round10}{\code{logical}, whether or not to round return value to nearest £10; default \code{TRUE}.

  \item{opts}{options, as created by \code{\link{tax_opts}()}, see details.} 

Fiscal/man/allowance.Rd

Lines 30 to 32 in e22ac22

	Argument \code{opts} specifying values for tax bands, rates and allowances must be provided using
	\code{\link{tax_opts}()}, which by default gives GOV.UK
	\href{https://www.gov.uk/government/publications/rates-and-allowances-income-tax/income-tax-rates-and-allowances-current-and-past}{values for 2025-2027 tax years}.

Argument \code{round10}, if \code{TRUE}, the default, causes the return value to be rounded to the nearest £10 in keeping with GOV.UK
\href{https://www.gov.uk/tax-codes/what-your-tax-code-means}{tax codes}.

Argument \code{opts} specifying values for tax bands, rates and allowances must be provided using
\code{\link{tax_opts}()}, which by default gives GOV.UK
\href{https://www.gov.uk/government/publications/rates-and-allowances-income-tax/income-tax-rates-and-allowances-current-and-past}{values for 2025-2027 tax years}.

[Mark-Eis]

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