This may not be the best answer but at least you can get an idea on how to work on
your report, and not using pivot.
SELECT A.[Category],
isnull(SUM([JANUARY]),'') as [JANUARY],
isnull(SUM([FEBRUARY]),'') as [FEBRUARY],
isnull(SUM([MARCH]),'') as [MARCH],
isnull(SUM([APRIL]),'') as [APRIL],
isnull(SUM([MAY]),'') as [MAY],
isnull(SUM([JUNE]),'') as [JUNE],
isnull(SUM([JULY]),'') as [JULY],
isnull(SUM([AUGUST]),'') as [AUGUST],
isnull(SUM([SEPTEMBER]),'') as [SEPTEMBER],
isnull(SUM([OCTOBER]),'') as [OCTOBER],
isnull(SUM([NOVEMBER]),'') as [NOVEMBER],
isnull(SUM([DECEMBER]),'') as [DECEMBER]
FROM (SELECT EXPENSERECORD.Category [Category],
CASE WHEN DATENAME(month, REVENUE.transactionDate) = 'January' THEN SUM(EXPENSERECORD.AMOUNT) END AS [JANUARY],
CASE WHEN DATENAME(month, REVENUE.transactionDate) = 'February' THEN SUM(EXPENSERECORD.AMOUNT) END AS [FEBRUARY],
CASE WHEN DATENAME(month, REVENUE.transactionDate) = 'March' THEN SUM(EXPENSERECORD.AMOUNT) END AS [March],
CASE WHEN DATENAME(month, REVENUE.transactionDate) = 'April' THEN SUM(EXPENSERECORD.AMOUNT) END AS [APRIL],
CASE WHEN DATENAME(month, REVENUE.transactionDate) = 'May' THEN SUM(EXPENSERECORD.AMOUNT) END AS [MAY],
CASE WHEN DATENAME(month, REVENUE.transactionDate) = 'June' THEN SUM(EXPENSERECORD.AMOUNT) END AS [JUNE],
CASE WHEN DATENAME(month, REVENUE.transactionDate) = 'July' THEN SUM(EXPENSERECORD.AMOUNT) END AS [JULY],
CASE WHEN DATENAME(month, REVENUE.transactionDate) = 'August' THEN SUM(EXPENSERECORD.AMOUNT) END AS [AUGUST],
CASE WHEN DATENAME(month, REVENUE.transactionDate) = 'September' THEN SUM(EXPENSERECORD.AMOUNT) END AS [SEPTEMBER],
CASE WHEN DATENAME(month, REVENUE.transactionDate) = 'October' THEN SUM(EXPENSERECORD.AMOUNT) END AS [OCTOBER],
CASE WHEN DATENAME(month, REVENUE.transactionDate) = 'November' THEN SUM(EXPENSERECORD.AMOUNT) END AS [NOVEMBER],
CASE WHEN DATENAME(month, REVENUE.transactionDate) = 'December' THEN SUM(EXPENSERECORD.AMOUNT) END AS [DECEMBER]
FROM REVENUE
LEFT JOIN EXPENSERECORD ON REVENUE.transactionID = EXPENSERECORD.transactionID
GROUP BY REVENUE.transactionDate, EXPENSERECORD.Category) A
WHERE A.Category IS NOT NULL
GROUP BY A.Category